In daemon mode, send error messages to parent to write them on stderr.

This allows to get a better error message than "Spawning the daemon failed."
when initialization fails.

The error message is sent through the pipe. When init is OK, just send
a null byte.
Only ignore files in top directory.

For some reason, git ignored all subdirectories. This fixes it.
Add and init script for debian.
Add a logrotate script.
Do not print daemon's pid after forking if a pidfile is used.
daemon, shairport: POSIX compatibility fix