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/RenderObject.h

@@ -189,9 +189,6 @@ public:
 
 	const RenderObject &operator=(const RenderObject &r);
 
-	void enableProjectCollision();
-	void disableProjectCollision();
-
 	void toggleCull(bool value);
 	
 	void safeKill();
@@ -293,8 +290,6 @@ public:
 
 	int collideRadius;
 	Vector collidePosition;
-	bool useCollisionMask;
-	//Vector collisionMaskHalfVector;
 	std::vector<Vector> collisionMask;
 	std::vector<Vector> transformedCollisionMask;