Added stack type enums to love.graphics.push (resolves issue #906.) Current enums are "transform" and "all". "transform" is the default (for compatibility.) When love.graphics.push("all") is used, love.graphics.pop() will restore all love.graphics module state to what it was when push was called.

Updated the graphics code to use a custom matrix stack rather than OpenGL1's APIs.

src/modules/graphics/opengl/Canvas.h

@@ -120,7 +120,6 @@ public:
 	static bool isFormatSupported(Format format);
 
 	static Canvas *current;
-	static void bindDefaultCanvas();
 
 	// The viewport dimensions of the system (default) framebuffer.
 	static OpenGL::Viewport systemViewport;