IRC.pm: Add publicmsg_cb, send_chan, send_srv methods.

publicmsg_cb method is getter and setter of publicmsg callback.
send_{chan,srv} methods are deletgator of AnyEvent::IRC::Client's same method.
Voice.pm: Add POD document.
Util.pm: Modify some tiny syntax.
Growl.pm: DEBUG print is output when only DEBUG environment is true.
Growl.pm: Fix typo of Cocoa::Growl using.
Sound.pm: Initial release.
Makefile.PL: includes "bin/stopwatch.pl" to EXE_FILES.