There's entries for header files we don't use, and the cvsimport doesn't
like removing files automatically, etc., and it won't have known to have
done this from autoconf's POV, so define that in the correct place, hence
the removal of the previously committed Makefile.

it, extended from a diff from George Nachman.

commands and allow a command to block execution of subsequent commands. This
allows run-shell and if-shell to be synchronous which has been much requested.

Each client has a default command queue and commands are consumed one at a time
from it. A command may suspend execution from the queue by returning
CMD_RETURN_WAIT and then resume it by calling cmd_continue() - for example
run-shell does this from the callback that is fired after the job is freed.

When the command queue becomes empty, command clients are automatically exited
(unless attaching). A callback is also fired - this is used for nested commands
in, for example, if-shell which can block execution of the client's cmdq until
a new cmdq becomes empty.

Also merge all the old error/info/print functions together and lose the old
curclient/cmdclient distinction - a cmdq is bound to one client (or none if in
the configuration file), this is a command client if c->session is NULL
otherwise an attached client.

Conflicts:
	Makefile
	grid-utf8.c

UTF-8, collapse the two together. Simplifies the code at the expense of
more memory (which can probably be reduced again later).

Sync from OpenBSD.

Make command exec functions return an enum rather than -1/0/1 values and
add a new value to mean "leave client running but don't attach" to fix
problems with using some commands in a command sequence. Most of the
work by Thomas Adam, problem reported by "jspenguin" on SF bug 3535531.