Rework group names: stash the group name inside the group_ctx as opposed
to having to manage an array outside in screen_ctx for group names and
shortcuts.  Simplifies (and moves bits for) reading, and constructing
data for, EWMH's _NET_DESKTOP_NAMES.
Move termpath and lockpath into cmdq; side effect is that 'lock' and
'term' now show up in the application menu.
style nit
generic sighandler
Few style nits; extend 'path' to MAXPATHLEN.
Get rid of a redundant array of groups per screen; we already have a
link to the group queue for each screen.
screen_fromroot -> screen_find
more style nits
Add screen_ctx to group_ctx, and populate on init.
Now that a group knows its screen, only pass down the group_ctx.
Remove duplicate client queue (mruq); instead, remove and take the
global Clientq and place it inside screen_ctx since every client belongs
to a screen, then use the same per screen clientq to track stacking
order (the sole reason for mruq).
since mruq has been folded in, rename mru-named functions
more style nits and wrapping
name the group client queue appropriately, like other queues
move the check for an empty queue up during cycle
fold in 'active' into 'flags'
Remove incorrect cast in kbfunc_exec. In kbfunc_ssh, reverse logic on
truncation check so it's obvious.