Add pane_dead_status for exit status of dead panes.
Only redraw affected lines when selection changes with mouse. From
Michael Graczyk.
Notify on zoom/unzoom, from George Nachmann.
Merge branch 'obsd-master'

Conflicts:
	format.c
Merge branch 'master' of ssh://git.code.sf.net/p/tmux/tmux-code
t_kP is the same as PageUp, so no need for it, from Daniel Hahler.
Merge branch 'master' of ssh://git.code.sf.net/p/tmux/tmux-code