monitor: Fix directory symlink deletion handling

When a symlink to a direcotry is deleted inotify cannot tell it from a
regular file rendering all its children orphans.
This sometimes leads to an unexpected effect - they may appear later in
a newly created directory when it gets an id used by the deleted symlink.

monitor.h

@@ -1,6 +1,7 @@
 int monitor_insert_file(const char *name, const char *path);
 int monitor_insert_directory(int fd, char *name, const char * path);
 int monitor_remove_file(const char * path);
+int monitor_remove_tree(const char * path);
 int monitor_remove_directory(int fd, const char * path);
 
 #if defined(HAVE_INOTIFY) || defined(HAVE_KQUEUE)