daemon: Debian/kFreeBSD 9.2 fails to compile due to caps

daemon: Debian/kFreeBSD 9.2 fails to compile due to caps

Debian/kFreeBSD 9.2 comes with sys/capability.h but it is not usable; work around it

the patch does several things:
* it makes the comment point to the correct bugtracker issue: https://bugs.freedesktop.org/show_bug.cgi?id=72580
* it handles Debian/kFreeBSD the same way as FreeBSD
* it logs a warning that capabilities are actually NOT dropped

daemon/caps.c: In function ‘pa_drop_caps’:
daemon/caps.c:93:2: error: #error "Don't know how to do capabilities on your system.  Please send a patch."
 #error "Don't know how to do capabilities on your system.  Please send a patch."
  ^
Makefile:9575: recipe for target 'daemon/pulseaudio-caps.o' failed

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>