Rename cache.[ch] to memcache.[ch]

cache.h conflicts with an XFS DMAPI include on "opi" :-(

source/include/includes.h

@@ -719,7 +719,7 @@ typedef char fstring[FSTRING_LEN];
 #include "packet.h"
 #include "ctdbd_conn.h"
 #include "talloc_stack.h"
-#include "cache.h"
+#include "memcache.h"
 
 /* used in net.c */
 struct functable {

source/include/memcache.h

@@ -17,8 +17,8 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef __CACHE_H__
-#define __CACHE_H__
+#ifndef __MEMCACHE_H__
+#define __MEMCACHE_H__
 
 #include "includes.h"
 

source/lib/memcache.c

@@ -17,7 +17,7 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include "cache.h"
+#include "memcache.h"
 #include "rbtree.h"
 
 struct memcache_element {