Plug small memory leak in run-shell

Don't potentially leak the command to run were it to fail.
Remove previous
Send DSC 1000p at the beginning of a -CC client's lifetime and ST and the end,
from George Nachman..
Add -q flags to shut up errors to capture-pane and show-options, from George
Nachman.
Remove some unused/unnecessary control notifications, from George Nachman.
tty.path can be NULL, don't dereference it. From George Nachman.
Print %%error not %%end guard on error, from George Nachman.
Preserve trailing spaces with capture-pane -J, from George Nachman.
Continue the parent cmdq after sourcing a file.
Add some additional debug logging.
Unzoom on last-pane and fix a typo, from Romain Francoise.
Do not leak command in formats, from Romain Francoise.
Merge branch 'master' of ssh://git.code.sf.net/p/tmux/tmux-code
Allow lastgc to be NULL in grid_string_cells so find-window doesn't crash,
problem reported by eugene everson.
Add a wait-for command which blocks a client on a named channel until it is
wokrn up again (with wait-for -S). From Thiago Padilha.
Add wait-for -L and -U for lock and unlock, from Thiago Padilha.
Fix --disable-static, reported by Shea Levy.
Rename session idx to session id throughout and add $ prefix to targets to use
it, extended from a diff from George Nachman.
Merge branch 'master' of ssh://git.code.sf.net/p/tmux/tmux-code
Do not redraw panes if invisible.