Merge pull request #522 from sephiroth99/lf3

Linux compilation/link and compatibility fixes

src/xenia/gpu/gl4/gl4_shader.h

@@ -29,7 +29,7 @@ class GL4Shader : public Shader {
   GLuint shader() const { return shader_; }
   GLuint vao() const { return vao_; }
 
-  bool Prepare();
+  bool Prepare() override;
 
  protected:
   bool PrepareVertexArrayObject();