LibAccelGfx+WebContent: Add GPU painter support on macOS

With these changes it is now possible to create OpenGL context on macOS
and run GPU-painter. For now only QT client has a CLI param that turns
it on though.

Userland/Libraries/LibAccelGfx/Painter.cpp

@@ -75,7 +75,7 @@ in vec2 vTextureCoord;
 uniform sampler2D uSampler;
 out vec4 fragColor;
 void main() {
-    fragColor = texture2D(uSampler, vTextureCoord) * uColor;
+    fragColor = texture(uSampler, vTextureCoord) * uColor;
 }
 )";