First, the existing sway_binding structure is given an
enumerated type code. As all flags to bindsym/bindcode
are boolean, a single uint32 is used to hold all flags.
The _BORDER, _CONTENTS, _TITLEBAR flags, when active,
indicate in which part of a container the binding can
trigger; to localize complexity, they do not overlap
with the command line arguments, which center around
_TITLEBAR being set by default.
The keyboard handling code is adjusted for this change,
as is binding_key_compare; note that BINDING_LOCKED
is *not* part of the key portion of the binding.
Next, list of mouse bindings is introduced and cleaned up.
Finally, the binding command parsing code is extended
to handle the case where bindsym is used to describe
a mouse binding rather than a keysym binding; the
difference between the two may be detected as late as
when the first key/button is parsed, or as early as
the first flag. As bindings can have multiple
keycodes/keysyms/buttons, mixed keysym/button sequences
are prohibited.