Fix mismatched class/struct definition warnings [-Wmismatched-tags]

Fixes the following Clang 7 warnings:
```
core/object.cpp:44:1: warning: '_ObjectDebugLock' defined as a struct here but previously declared as a class [-Wmismatched-tags]
core/variant_call.cpp:43:1: warning: '_VariantCall' defined as a struct here but previously declared as a class [-Wmismatched-tags]
drivers/gles3/rasterizer_storage_gles3.h:765:2: warning: 'MultiMesh' defined as a struct here but previously declared as a class [-Wmismatched-tags]
editor/editor_node.h:794:1: warning: 'EditorProgress' defined as a struct here but previously declared as a class [-Wmismatched-tags]
modules/bullet/rigid_body_bullet.h:230:17: warning: class 'KinematicUtilities' was previously declared as a struct [-Wmismatched-tags]
modules/bullet/space_bullet.h:60:1: warning: class 'btSoftBodyWorldInfo' was previously declared as a struct [-Wmismatched-tags]
scene/resources/world_2d.cpp:40:1: warning: 'SpatialIndexer2D' defined as a struct here but previously declared as a class [-Wmismatched-tags]
scene/resources/world.cpp:39:1: warning: 'SpatialIndexer' defined as a struct here but previously declared as a class [-Wmismatched-tags]
servers/audio/reverb_sw.cpp:60:1: warning: 'ReverbParamsSW' defined as a struct here but previously declared as a class [-Wmismatched-tags]
thirdparty/bullet/BulletSoftBody/btSoftBody.h:43:1: warning: 'btSoftBodyWorldInfo' defined as a struct here but previously declared as a class [-Wmismatched-tags]
```

2 files changed, 6 insertions, 18 deletions

diff --git a/servers/audio/reverb_sw.cpp b/servers/audio/reverb_sw.cpp
index 13742d5db5..d078da38b4 100644
--- a/servers/audio/reverb_sw.cpp
+++ b/servers/audio/reverb_sw.cpp
@@ -29,33 +29,21 @@
 /*************************************************************************/
 
 #include "reverb_sw.h"
+
 #include "core/print_string.h"
-#include "stdlib.h"
+
+#include <stdlib.h>
+
 #define SETMIN(x, y) (x) = MIN((x), (y))
+
 #define rangeloop(c, min, max) \
 	for ((c) = (min); (c) < (max); (c)++)
 
 #define ABSDIFF(x, y) \
 	(((x) < (y)) ? ((y) - (x)) : ((x) - (y)))
 
-#ifdef bleh_MSC_VER
-
-#if _MSC_VER >= 1400
-_FORCE_INLINE_ int32_tMULSHIFT_S32(
-		int32_t Factor1,
-		int32_t Factor2,
-		uint8_t Bits) {
-
-	return __ll_rshift(
-			__emul(Factor1, Factor2),
-			Bits);
-}
-#endif
-
-#else
 #define MULSHIFT_S32(Factor1, Factor2, Bits) \
 	((int)(((int64_t)(Factor1) * (Factor2)) >> (Bits)))
-#endif
 
 struct ReverbParamsSW {
 	unsigned int BufferSize; // Required buffer size
diff --git a/servers/audio/reverb_sw.h b/servers/audio/reverb_sw.h
index 26b3fa5166..01977d1f61 100644
--- a/servers/audio/reverb_sw.h
+++ b/servers/audio/reverb_sw.h
@@ -34,7 +34,7 @@
 #include "core/os/memory.h"
 #include "core/typedefs.h"
 
-class ReverbParamsSW;
+struct ReverbParamsSW;
 
 class ReverbSW {
 public: