Fix warnings about set but unused variables [-Wunused-but-set-variable]

Fixes the following GCC 5 warnings:
```
drivers/gles2/rasterizer_canvas_gles2.cpp:814:8: warning: variable 'rt_size' set but not used [-Wunused-but-set-variable]
drivers/gles2/rasterizer_scene_gles2.cpp:2270:11: warning: variable 'vp_height' set but not used [-Wunused-but-set-variable]
drivers/gles2/rasterizer_scene_gles2.cpp:2673:22: warning: variable 'e' set but not used [-Wunused-but-set-variable]
drivers/gles2/rasterizer_scene_gles2.cpp:715:7: warning: variable 'no_cull' set but not used [-Wunused-but-set-variable]
drivers/gles2/shader_gles2.cpp:693:14: warning: variable 'cc' set but not used [-Wunused-but-set-variable]
drivers/gles3/rasterizer_canvas_gles3.cpp:1226:8: warning: variable 'rt_size' set but not used [-Wunused-but-set-variable]
drivers/gles3/rasterizer_scene_gles3.cpp:3039:10: warning: variable 'contrib' set but not used [-Wunused-but-set-variable]
drivers/gles3/rasterizer_scene_gles3.cpp:4504:32: warning: variable 'vp_height' set but not used [-Wunused-but-set-variable]
editor/editor_inspector.cpp:272:9: warning: variable 'guide_color' set but not used [-Wunused-but-set-variable]
editor/editor_themes.cpp:1067:14: warning: variable 'alpha3' set but not used [-Wunused-but-set-variable]
editor/editor_themes.cpp:263:8: warning: variable 'script_bg_color' set but not used [-Wunused-but-set-variable]
editor/plugins/collision_shape_2d_editor_plugin.cpp:326:11: warning: variable 'cpoint' set but not used [-Wunused-but-set-variable]
editor/plugins/mesh_editor_plugin.cpp:72:9: warning: variable 'size' set but not used [-Wunused-but-set-variable]
editor/plugins/shader_editor_plugin.cpp:471:12: warning: variable 'mpos' set but not used [-Wunused-but-set-variable]
editor/plugins/shader_editor_plugin.cpp:89:8: warning: variable 'basetype_color' set but not used [-Wunused-but-set-variable]
editor/plugins/shader_editor_plugin.cpp:90:8: warning: variable 'type_color' set but not used [-Wunused-but-set-variable]
editor/plugins/shader_editor_plugin.cpp:92:8: warning: variable 'string_color' set but not used [-Wunused-but-set-variable]
modules/visual_script/visual_script_editor.cpp:2521:7: warning: variable 'seq_connect' set but not used [-Wunused-but-set-variable]
platform/android/export/export.cpp:580:12: warning: variable 'styles_count' set but not used [-Wunused-but-set-variable]
platform/android/export/export.cpp:584:12: warning: variable 'styles_offset' set but not used [-Wunused-but-set-variable]
platform/osx/export/export.cpp:464:9: warning: variable 'zerr' set but not used [-Wunused-but-set-variable]
scene/2d/tile_map.cpp:260:10: warning: variable 'tcenter' set but not used [-Wunused-but-set-variable]
scene/3d/light.cpp:166:7: warning: variable 'editor_ok' set but not used [-Wunused-but-set-variable]
scene/3d/navigation.cpp:566:11: warning: variable 'closest_navmesh' set but not used [-Wunused-but-set-variable]
scene/gui/rich_text_label.cpp:869:8: warning: variable 'size' set but not used [-Wunused-but-set-variable]
scene/main/viewport.cpp:705:14: warning: variable 'xform' set but not used [-Wunused-but-set-variable]
scene/main/viewport.cpp:706:8: warning: variable 'ss' set but not used [-Wunused-but-set-variable]
scene/main/viewport.cpp:726:14: warning: variable 'xform' set but not used [-Wunused-but-set-variable]
scene/main/viewport.cpp:727:8: warning: variable 'ss' set but not used [-Wunused-but-set-variable]
scene/resources/material.cpp:430:7: warning: variable 'using_world' set but not used [-Wunused-but-set-variable]
servers/visual/shader_language.cpp:2026:7: warning: variable 'all_const' set but not used [-Wunused-but-set-variable]
servers/visual/visual_server_scene.cpp:1383:28: warning: variable 'z_max_cam' set but not used [-Wunused-but-set-variable]
```

Also fixes two [-Wunused-value] warnings:
```
scene/gui/text_edit.cpp:4405:20: warning: statement has no effect [-Wunused-value]
servers/visual/visual_server_scene.cpp:905:48: warning: value computed is not used [-Wunused-value]
```

Some of those are bugs and need further work, they are identified with
`// FIXME` comments.

3 files changed, 0 insertions, 29 deletions

diff --git a/editor/plugins/collision_shape_2d_editor_plugin.cpp b/editor/plugins/collision_shape_2d_editor_plugin.cpp
index e3f364790a..d1a94f5b49 100644
--- a/editor/plugins/collision_shape_2d_editor_plugin.cpp
+++ b/editor/plugins/collision_shape_2d_editor_plugin.cpp
@@ -323,7 +323,6 @@ bool CollisionShape2DEditor::forward_canvas_gui_input(const Ref<InputEvent> &p_e
 	if (mb.is_valid()) {
 
 		Vector2 gpoint = mb->get_position();
-		Vector2 cpoint = node->get_global_transform().affine_inverse().xform(canvas_item_editor->snap_point(canvas_item_editor->get_canvas_transform().affine_inverse().xform(mb->get_position())));
 
 		if (mb->get_button_index() == BUTTON_LEFT) {
 			if (mb->is_pressed()) {
diff --git a/editor/plugins/mesh_editor_plugin.cpp b/editor/plugins/mesh_editor_plugin.cpp
index 7b7e23531a..73a216e96f 100644
--- a/editor/plugins/mesh_editor_plugin.cpp
+++ b/editor/plugins/mesh_editor_plugin.cpp
@@ -65,14 +65,6 @@ void MeshEditor::_notification(int p_what) {
 			first_enter = false;
 		}
 	}
-
-	if (p_what == NOTIFICATION_DRAW) {
-
-		Ref<Texture> checkerboard = get_icon("Checkerboard", "EditorIcons");
-		Size2 size = get_size();
-
-		//draw_texture_rect(checkerboard, Rect2(Point2(), size), true);
-	}
 }
 
 void MeshEditor::_update_rotation() {
diff --git a/editor/plugins/shader_editor_plugin.cpp b/editor/plugins/shader_editor_plugin.cpp
index 361271af89..775fca308e 100644
--- a/editor/plugins/shader_editor_plugin.cpp
+++ b/editor/plugins/shader_editor_plugin.cpp
@@ -86,10 +86,7 @@ void ShaderTextEditor::_load_theme_settings() {
 	Color search_result_border_color = EDITOR_GET("text_editor/highlighting/search_result_border_color");
 	Color symbol_color = EDITOR_GET("text_editor/highlighting/symbol_color");
 	Color keyword_color = EDITOR_GET("text_editor/highlighting/keyword_color");
-	Color basetype_color = EDITOR_GET("text_editor/highlighting/base_type_color");
-	Color type_color = EDITOR_GET("text_editor/highlighting/engine_type_color");
 	Color comment_color = EDITOR_GET("text_editor/highlighting/comment_color");
-	Color string_color = EDITOR_GET("text_editor/highlighting/string_color");
 
 	get_text_edit()->add_color_override("background_color", background_color);
 	get_text_edit()->add_color_override("completion_background_color", completion_background_color);
@@ -140,26 +137,9 @@ void ShaderTextEditor::_load_theme_settings() {
 		get_text_edit()->add_keyword_color(E->get(), keyword_color);
 	}
 
-	//colorize core types
-	//Color basetype_color= EDITOR_DEF("text_editor/base_type_color",Color(0.3,0.3,0.0));
-
 	//colorize comments
 	get_text_edit()->add_color_region("/*", "*/", comment_color, false);
 	get_text_edit()->add_color_region("//", "", comment_color, false);
-
-	/*//colorize strings
-	Color string_color = EDITOR_DEF("text_editor/string_color",Color::hex(0x6b6f00ff));
-
-	List<String> strings;
-	shader->get_shader_mode()->get_string_delimiters(&strings);
-
-	for (List<String>::Element *E=strings.front();E;E=E->next()) {
-
-		String string = E->get();
-		String beg = string.get_slice(" ",0);
-		String end = string.get_slice_count(" ")>1?string.get_slice(" ",1):String();
-		get_text_edit()->add_color_region(beg,end,string_color,end=="");
-	}*/
 }
 
 void ShaderTextEditor::_check_shader_mode() {