Improvement: --blur-background-exclude #98 & MESA_swap_control & others

- Add --blur-background-exclude. (#98)

- Add `opengl-mswc` VSync, which uses MESA_swap_control instead of
  SGI_swap_control. I don't expect it to perform better than
  SGI_swap_control, though.

- Update CMakeLists.txt .

- Add a few targets for D-Bus `win_get`. Misc changes.

- Known issue: Apparently I've forgotten implementing --inactive-dim on
  GLX backend... Silly me.

compton.sample.conf

@@ -25,6 +25,7 @@ alpha-step = 0.06;
 # blur-background = true;
 # blur-background-frame = true;
 blur-background-fixed = false;
+blur-background-exclude = [ "window_type = 'dock'", "window_type = 'desktop'" ];
 
 # Fading
 fading = true;