Separate platform indepenent code into monitor.c, and move inotify(7)

specific code to monitor_inotify.c.
Both monitor_inotify.c and monitor_kqueue.c provide their functions
for adding and removing watches. Prefix these functions with monitor_.

Makefile.am

@@ -36,6 +36,10 @@ else
 minidlnad_SOURCES += select.c
 endif
 
+if HAVE_INOTIFY
+minidlnad_SOURCES += monitor_inotify.c
+endif
+
 if HAVE_VORBISFILE
 vorbislibs = -lvorbis -logg
 else