Give nbtree move right function internal linkage.

Declare _bt_moveright() static.  This is a minor modularity win; the
routine was already private to nbtsearch.c for all practical purposes.

Author: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://postgr.es/m/CAEze2WgWVzCNEXQB_op5MMZMDgJ3fg3AhVm6bq2iZPpJNXGhWw@mail.gmail.com

Author: petergeoghegan

src/backend/access/nbtree/nbtsearch.c

@@ -26,6 +26,9 @@
 
 
 static void _bt_drop_lock_and_maybe_pin(IndexScanDesc scan, BTScanPos sp);
+static Buffer _bt_moveright(Relation rel, Relation heaprel, BTScanInsert key,
+							Buffer buf, bool forupdate, BTStack stack,
+							int access);
 static OffsetNumber _bt_binsrch(Relation rel, BTScanInsert key, Buffer buf);
 static int	_bt_binsrch_posting(BTScanInsert key, Page page,
 								OffsetNumber offnum);
@@ -231,7 +234,7 @@ _bt_search(Relation rel, Relation heaprel, BTScanInsert key, Buffer *bufP,
  * 'access'.  If we move right, we release the buffer and lock and acquire
  * the same on the right sibling.  Return value is the buffer we stop at.
  */
-Buffer
+static Buffer
 _bt_moveright(Relation rel,
 			  Relation heaprel,
 			  BTScanInsert key,

src/include/access/nbtree.h

@@ -1272,9 +1272,6 @@ extern void _bt_pendingfsm_finalize(Relation rel, BTVacState *vstate);
  */
 extern BTStack _bt_search(Relation rel, Relation heaprel, BTScanInsert key,
 						  Buffer *bufP, int access);
-extern Buffer _bt_moveright(Relation rel, Relation heaprel, BTScanInsert key,
-							Buffer buf, bool forupdate, BTStack stack,
-							int access);
 extern OffsetNumber _bt_binsrch_insert(Relation rel, BTInsertState insertstate);
 extern int32 _bt_compare(Relation rel, BTScanInsert key, Page page, OffsetNumber offnum);
 extern bool _bt_first(IndexScanDesc scan, ScanDirection dir);