Add CMakeLists.txt to support building with CMake, as @pvanek requests.
The old Makefile system and CPackConfig.cmake are still usable. (Of
course, make sure you don't overwrite them by executing cmake.) There
must be a bunch of bugs in CMakeLists.txt. :-) Let chjj decide which one
he will choose, here I keep both.
- Let window type detection start with the client window if there's one,
in hope to enhance performance.
- Change get_wintype_prop() to fetch the property only once.
- Default to WINTYPE_UNKNOWN instead of WINTYPE_NORMAL if
_NET_WM_WINDOW_TYPE is missing.
- Fix a mistake in calc_opacity().
- Add some items to .gitignore.
- Fix a typo in usage().
Richard Grenville