Use _XPG6 on Solaris with GCC because the headers are insane and don't like GCC
with -std=gnu99 and _XPG4_2. We should not really be using _XPG* at all but
there doesn't seem to be a magic define that says "give me the latest
standard", and things are further confused by the CMSG_DATA check in
configure.ac which sets _XOPEN_SOURCE _XOPEN_SOURCE_EXTENDED.

While here add COPYING to EXTRA_DIST.
Don't set TMUX_CONF in tmux.h.
Merge branch 'master' of ssh://git.code.sf.net/p/tmux/tmux-code
+strings.h in compat/.
Mark control commands specially so the client can identify them, based
on a diff from George Nachman a while back.
Always push a focus event when the application turns it on, prompted by
discussion with Hayaki Saito a while ago.
Focus events can cause trouble if left on and they can't be turned off
during idle periods (like the other states are) because we'd miss
events. So add a server option to control them. Defaults to off.