meta: Rewrite sowm and swap to XCB.

This was my first real C project and it shows. Learning C is quite
fun and I still have a long way to go. This next rewrite should be
less of a hot-mess than the original Xlib version.

Notable mistakes:

- while (1 && ...)
- for win (spastic pre-processor stuff)
- no proper tracking of client sizes/positions.
- lazy window focus model.
- almost code-golfed code-base.
- circular-doubly-linked-list for clients.

The following changes mark the initial commit for the rewrite.
The window manager works but does not yet do enough for it to be
usable. Clients, keybindings, a configuration file, etc, etc do
not yet exist. Baby steps.

.gitignore

@@ -1,3 +1,4 @@
 sowm
 sowm.o
 config.h
+.ccls-cache