expose common extensions for image/movie/audio types, since python scripts had to do this internally.

- bpy.path.extensions_image
- bpy.path.extensions_movie
- bpy.path.extensions_audio

eg:

  if os.path.splitext(filename)[1].lower() in bpy.path.extensions_image:
      ... we have an image ...

source/blender/python/intern/CMakeLists.txt

@@ -56,6 +56,7 @@ set(SRC
 	bpy_library.c
 	bpy_operator.c
 	bpy_operator_wrap.c
+	bpy_path.c
 	bpy_props.c
 	bpy_rna.c
 	bpy_rna_anim.c
@@ -76,6 +77,7 @@ set(SRC
 	bpy_library.h
 	bpy_operator.h
 	bpy_operator_wrap.h
+	bpy_path.h
 	bpy_props.h
 	bpy_rna.h
 	bpy_rna_anim.h

source/blender/python/intern/bpy_interface.c

@@ -44,6 +44,7 @@
 #include "bpy.h"
 #include "gpu.h"
 #include "bpy_rna.h"
+#include "bpy_path.h"
 #include "bpy_util.h"
 #include "bpy_traceback.h"
 #include "bpy_intern_string.h"
@@ -212,6 +213,7 @@ static struct _inittab bpy_internal_modules[] = {
 	{(char *)"mathutils", PyInit_mathutils},
 //	{(char *)"mathutils.geometry", PyInit_mathutils_geometry},
 //	{(char *)"mathutils.noise", PyInit_mathutils_noise},
+	{(char *)"_bpy_path", BPyInit__bpy_path},
 	{(char *)"bgl", BPyInit_bgl},
 	{(char *)"blf", BPyInit_blf},
 	{(char *)"bmesh", BPyInit_bmesh},