Added locking to SpriteBatch, and conf.lua.

src/modules/graphics/opengl/SpriteBatch.h

@@ -68,6 +68,9 @@ namespace opengl
 		int usage;
 		int gl_usage;
 
+		// If the buffer is locked, this pointer is nonzero.
+		vertex * lockp;
+
 	public:
 
 		enum UsageHint
@@ -85,6 +88,9 @@ namespace opengl
 		//void addf(float x, float y, float a, float sx, float sy, float ox, float oy, Frame * frame);
 		void clear();
 
+		void * lock();
+		void unlock();
+
 		// Implements Drawable.
 		void draw(float x, float y, float angle, float sx, float sy, float ox, float oy) const;