Forward declaration must match eventual function - both must be static

Refs trac:3763

This commit was SVN r30082.

The following Trac tickets were found above:
  Ticket 3763 --> https://svn.open-mpi.org/trac/ompi/ticket/3763

oshmem/mca/memheap/base/memheap_base_mkey.c

@@ -67,7 +67,7 @@ struct oob_comm memheap_oob;
 
 static int send_buffer(int pe, opal_buffer_t *msg);
 
-int oshmem_mkey_recv_cb(void);
+static int oshmem_mkey_recv_cb(void);
 
 /* pickup list of rkeys and remote va */
 static int memheap_oob_get_mkeys(int pe,