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/SpriteBatch.cpp

@@ -271,11 +271,10 @@ void SpriteBatch::draw(float x, float y, float angle, float sx, float sy, float
 		return;
 
 	static Matrix t;
-
-	glPushMatrix();
-
 	t.setTransformation(x, y, angle, sx, sy, ox, oy, kx, ky);
-	glMultMatrixf((const GLfloat *)t.getElements());
+
+	OpenGL::TempTransform transform(gl);
+	transform.get() *= t;
 
 	texture->predraw();
 
@@ -314,8 +313,6 @@ void SpriteBatch::draw(float x, float y, float angle, float sx, float sy, float
 	}
 
 	texture->postdraw();
-
-	glPopMatrix();
 }
 
 void SpriteBatch::addv(const Vertex *v, int index)