Added love.graphics.intersectScissor(x, y, w, h). Resolves issue #1071.

It sets the active scissor rectangle to the intersection of the existing scissor (if any) and the specified rectangle.

src/modules/graphics/opengl/wrap_Graphics.h

@@ -52,6 +52,7 @@ int w_getWidth(lua_State *L);
 int w_getHeight(lua_State *L);
 int w_getDimensions(lua_State *L);
 int w_setScissor(lua_State *L);
+int w_intersectScissor(lua_State *L);
 int w_getScissor(lua_State *L);
 int w_stencil(lua_State *L);
 int w_setStencilTest(lua_State *L);