native LIRC support for ncmpc

native LIRC support for ncmpc

The attachment includes the patch and a sample .lircrc config for
testing purposes (i. e. only a few commands are mapped to IR events).
The config is rather simple to write: For each button add a block like
this to ~/.lircrc:

begin
     button = <button name from /etc/lircd.conf>
     prog = ncmpc
     config = <command name from src/command.c>
end

The patch is not finished, there are several problems that still need to
be solved:

1. the configure.ac modifications are just for testing purposes and
should be made optional with a parameter like --enable-lirc
for ./configure. Unfortunately I'm not an expert on autoconfig tools.

2. LIRC example code [1] suggests looping over lirc_code2char, probably
to have multiple actions that can be triggered from one button. Perhaps
lirc_event(...) should be moved to lirc.c and be heavily modified, no
longer being a mere copy of keyboard_event(...).