Transmit arbitrary arguments when launching coq process

Arguments passed to :CoqLaunch are transmitted to coqtop.

Signed-off-by: Frederic Bour <frederic.bour@lakaban.net>
Add filename completion and expansion to :CoqLaunch

Signed-off-by: Frederic Bour <frederic.bour@lakaban.net>
Ignore "ctrl-c" (SIGINT) in coq process.