pointer: Remove focus method from handler
example/wm: Don't need to initialize shm (done by swc now)
bindings: Use an enum for modifiers
binding: Adjust interface to more easily support button and axis bindings
bindings: Add state parameter

This way, bindings can respond to key/button presses, releases, or both.
example/wm: Use local swc.h header
bindings: Add some comments about which keysyms are used