Misc code cleanups, little SkeletalSprite loading improvement.

- Removed some unused member variables.

- The BBGE_BUILD_WIDESCREEN define is now gone.

- Added an TiXMLDocument cache to prevent parsing the same file
once for each entity on the map with the same skeletal.

- Removed Lua func entity_warpToPathStart, which was essentially a no-op
because Entity::followingPath was always NULL. Removed related code.

- Set texture wrap only when required.

(Some changes taken from https://bitbucket.org/mattbierner/ios-aquaria,
special thanks for changeset 72d6460d9e60)

BBGE/Texture.h

@@ -62,9 +62,8 @@ public:
 	static ImageTGA *TGAloadMem(void *mem, int size);
 	
 	static bool useMipMaps;
-	bool repeat;
+	bool repeat, repeating;
 
-	int components;
 #ifdef BBGE_BUILD_OPENGL
 	static GLint filter;
 	static GLint format;