[GPU] Common resolve code based on compute shaders, swap MSAA samples 1 and 2, change ROV write rounding, random refactoring

src/xenia/gpu/gpu_flags.h

@@ -20,6 +20,8 @@ DECLARE_bool(vsync);
 
 DECLARE_bool(gpu_allow_invalid_fetch_constants);
 
+DECLARE_bool(half_pixel_offset);
+
 DECLARE_int32(query_occlusion_fake_sample_count);
 
 #endif  // XENIA_GPU_GPU_FLAGS_H_