Added Transform objects to love.math (resolves issue #1228).

- Added love.math.newTransform.
- Added love.graphics.applyTransform and love.graphics.replaceTransform.
- love.graphics.draw/print/printf, Text:add/addf, and SpriteBatch:add can accept a Transform argument.
- love.graphics.push can accept an optional Transform as a second argument, which will apply the Transform after pushing the matrix stack,
- Shader:send can accept Transform objects when sending to a mat4 uniform variable.

--HG--
branch : minor

src/modules/graphics/opengl/Graphics.h

@@ -38,6 +38,8 @@
 
 #include "video/VideoStream.h"
 
+#include "math/Transform.h"
+
 #include "Font.h"
 #include "Image.h"
 #include "graphics/Quad.h"
@@ -488,6 +490,10 @@ public:
 	void translate(float x, float y);
 	void shear(float kx, float ky);
 	void origin();
+
+	void applyTransform(love::math::Transform *transform);
+	void replaceTransform(love::math::Transform *transform);
+
 	Vector transformPoint(Vector point);
 	Vector inverseTransformPoint(Vector point);