allow the Bullet world importer to save a copy with swapped endianness

See http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=8191

Extras/Serialize/BulletWorldImporter/btBulletWorldImporter.h

@@ -47,7 +47,9 @@ public:
 
 	virtual ~btBulletWorldImporter();
 
-	bool	loadFile(const char* fileName);
+	///if you pass a valid preSwapFilenameOut, it will save a new file with a different endianness 
+	///this pre-swapped file can be loaded without swapping on a target platform of different endianness
+	bool	loadFile(const char* fileName, const char* preSwapFilenameOut=0);
 
 	///the memoryBuffer might be modified (for example if endian swaps are necessary)
 	bool	loadFileFromMemory(char *memoryBuffer, int len);