Add args parsing callback for some future work, currently unused.

Hide struct args behind a couple of accessor functions.

Also move cmdq_item and cmdq_list into cmd-queue.c (this is to make its
use more clearly defined and preparation for some future work).

Make struct cmd local to cmd.c and move it out of tmux.h.

Add a cmdq_continue function rather than twiddling the flag directly.

There is no reason wait-for has to be restricted to outside tmux.

Mass rename struct cmd_q to struct cmdq_item and related.

Rewrite command queue handling. Each client still has a command queue,
but there is also now a global command queue. Instead of command queues
being dispatched on demand from wherever the command hap

Rewrite command queue handling. Each client still has a command queue,
but there is also now a global command queue. Instead of command queues
being dispatched on demand from wherever the command happens to be
added, they are now all dispatched from the top level server
loop. Command queues may now also include callbacks as well as commands,
and items may be inserted after the current command as well as at the end.

This all makes command queues significantly more predictable and easier
to use, and avoids the complex multiple nested command queues used by
source-file, if-shell and friends.

A mass rename of struct cmdq to a better name (cmdq_item probably) is
coming.

show more ...

Add static in cmd-* and fix a few other nits.

I no longer use my SourceForge address so replace it.

Use member names in cmd_entry definitions so I stop getting confused
about the order.

Use __unused rather than rolling our own.

Use client pointer not file descriptor in logging.

Set woken flag when flushing so that the channel is freed, while here
use the same loop construct for both loops.

Change wait-for to work when the signal comes before the wait, also use
some helper functions and add some logging.

Instead of setting up the default keys by building the key struct
directly with a helper function in the cmd_entry, include a table of
bind-key commands and pass them through the command parser and a

Instead of setting up the default keys by building the key struct
directly with a helper function in the cmd_entry, include a table of
bind-key commands and pass them through the command parser and a
temporary cmd_q.

As well as being smaller, this will allow default bindings to be command
sequences which will probably be needed soon.

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Wake up any clients waiting with the wait-for command when the server
exits.

Various minor style and spacing nits.

Mark flags as optional and mutually exclusive. From Tiago Cunha.

Remove the barely-used and unnecessary command check() function.

Add wait-for -L and -U for lock and unlock, from Thiago Padilha.

Add a wait-for command which blocks a client on a named channel until it
is woken up again (with wait-for -S). From Thiago Padilha.