Introduce prototype-style function definition for sem_unlink.  This
happened upstream as part of:

commit e4f639e4a106d90c6f3159230788653fd6e40a26
Author: Roland McGrath <roland@hack.frob.com>
Date:   Fri Dec 12 13:17:21 2014 -0800

    NPTL: Refactor named semaphore code to use shm-directory.h

diff --git a/nptl/sem_unlink.c b/nptl/sem_unlink.c
index 610d82e7a6fe5bd1..1523522c41a52d76 100644
--- a/nptl/sem_unlink.c
+++ b/nptl/sem_unlink.c
@@ -25,8 +25,7 @@
 
 
 int
-sem_unlink (name)
-     const char *name;
+sem_unlink (const char *name)
 {
   char *fname;
   size_t namelen;