Fix some compiler warnings that have crept up recently.

Clean up after commits e40e78fa, 038aa959, 859d6592 and a21da89e.
Tut tut.

src/backend/access/transam/xlog.c

@@ -129,7 +129,6 @@ bool		XLOG_DEBUG = false;
 /* these are derived from XLOG_sync_method by assign_xlog_sync_method */
 int			sync_method = DEFAULT_SYNC_METHOD;
 static int	open_sync_bit = DEFAULT_SYNC_FLAGBIT;
-static Relation	XLogSaveBufferForHint_Relation = NULL;
 
 /*
  * walreceiver process receives xlog data from walsender process.

src/backend/cdb/dispatcher/cdbgang.c

@@ -99,7 +99,9 @@ static CdbComponentDatabaseInfo *findDatabaseInfoBySegIndex(
 		CdbComponentDatabases *cdbs, int segIndex);
 static void addGangToAllocated(Gang *gp);
 static Gang *getAvailableGang(GangType type, int size, int content);
+#ifdef USE_ASSERT_CHECKING
 static bool readerGangsExist(void);
+#endif
 
 /*
  * Create a reader gang.

src/backend/executor/nodePartitionSelector.c

@@ -259,7 +259,7 @@ ExecPartitionSelector(PartitionSelectorState *node)
 	return candidateOutputSlot;
 }
 
-static void LogSelectedPartitionsForScan(int32 selectorId, const HTAB *pidIndex, const int32 scanId);
+static void LogSelectedPartitionsForScan(int32 selectorId, HTAB *pidIndex, const int32 scanId);
 
 void LogPartitionSelection(EState *estate, int32 selectorId)
 {
@@ -283,7 +283,7 @@ void LogPartitionSelection(EState *estate, int32 selectorId)
 	}
 }
 
-void LogSelectedPartitionsForScan(int32 selectorId, const HTAB *pidIndex, const int32 scanId)
+void LogSelectedPartitionsForScan(int32 selectorId, HTAB *pidIndex, const int32 scanId)
 {
 	int32 numPartitionsSelected = 0;
 	Datum *selectedPartOids = palloc(sizeof(Datum) * hash_get_num_entries(pidIndex));

src/backend/optimizer/util/walkers.c

@@ -8,6 +8,7 @@
 #include "postgres.h"
 
 #include "miscadmin.h"
+#include "nodes/nodeFuncs.h"
 #include "optimizer/walkers.h"
 #include "optimizer/var.h"