Improve SDL & OpenGL backends

[Fusioon]

Most important fix: autocomplete resize bug

• This seem to be fixed by SDL_SyncWindow and calling mMovedFunc inside Resize

Other stuff:

• Implements "dynamic" texture that is used by about window
• Adds GL debug messenger in debug builds
• Removes need to link with -lgl
• Add ``SdlBFWindow::Show(ShowKind showKind)andSetForeground`
• Add GLRenderWindow::GetRefreshRate()
• Implements all? RenderState changes

Also I have noticed that on wayland the window resizing (by grabbing it's corner) most of the time does not send resize events in real time and seems that it cannot be worked around by using SDL_AddEventWatch, the events are generated only after the window is resized (mouse up)

[zerkawei]

Thanks for your contributions. Regarding window resizing, I searched a bit because I believed it worked before and it seems there was a regression in SDL (libsdl-org/SDL#14811) that looks like it could have caused this. The fix is not yet in a proper release but the issue may be fixed with a future version of SDL.