* syscalls.cc (check_dir_not_empty): New static function.
(unlink_nt): Move code checking for non-empty dir to check_dir_not_empty
and call check_dir_not_empty instead.
(rename): Add fault handler. Check oldpath and newpath for trailing
. and .. path components and return EINVAL if so. Check oldpath
for being on a vrtual file system. If renaming a dir fails with
STATUS_ACCESS_DENIED, check if the target dir is non-empty and return
ENOTEMPTY if so.
