Clean up most -Wunused-but-set-variable warnings from gcc 4.6

This warning is new in gcc 4.6 and part of -Wall.  This patch cleans
up most of the noise, but there are some still warnings that are
trickier to remove.

src/backend/commands/explain.c

@@ -1269,7 +1269,6 @@ show_plan_tlist(PlanState *planstate, List *ancestors, ExplainState *es)
 	List	   *result = NIL;
 	bool		useprefix;
 	ListCell   *lc;
-	int			i;
 
 	/* No work if empty tlist (this occurs eg in bitmap indexscans) */
 	if (plan->targetlist == NIL)
@@ -1290,7 +1289,6 @@ show_plan_tlist(PlanState *planstate, List *ancestors, ExplainState *es)
 	useprefix = list_length(es->rtable) > 1;
 
 	/* Deparse each result column (we now include resjunk ones) */
-	i = 0;
 	foreach(lc, plan->targetlist)
 	{
 		TargetEntry *tle = (TargetEntry *) lfirst(lc);

src/backend/commands/tablecmds.c

@@ -8164,14 +8164,12 @@ MergeAttributesIntoExisting(Relation child_rel, Relation parent_rel)
 	AttrNumber	parent_attno;
 	int			parent_natts;
 	TupleDesc	tupleDesc;
-	TupleConstr *constr;
 	HeapTuple	tuple;
 
 	attrrel = heap_open(AttributeRelationId, RowExclusiveLock);
 
 	tupleDesc = RelationGetDescr(parent_rel);
 	parent_natts = tupleDesc->natts;
-	constr = tupleDesc->constr;
 
 	for (parent_attno = 1; parent_attno <= parent_natts; parent_attno++)
 	{

src/backend/commands/tsearchcmds.c

@@ -2156,14 +2156,12 @@ DropConfigurationMapping(AlterTSConfigurationStmt *stmt,
 	HeapTuple	maptup;
 	int			i;
 	Oid			prsId;
-	int		   *tokens,
-				ntoken;
+	int		   *tokens;
 	ListCell   *c;
 
 	prsId = ((Form_pg_ts_config) GETSTRUCT(tup))->cfgparser;
 
 	tokens = getTokenTypes(prsId, stmt->tokentype);
-	ntoken = list_length(stmt->tokentype);
 
 	i = 0;
 	foreach(c, stmt->tokentype)

src/backend/commands/vacuum.c

@@ -92,8 +92,7 @@ vacuum(VacuumStmt *vacstmt, Oid relid, bool do_toast,
 	   BufferAccessStrategy bstrategy, bool for_wraparound, bool isTopLevel)
 {
 	const char *stmttype;
-	volatile bool all_rels,
-				in_outer_xact,
+	volatile bool in_outer_xact,
 				use_own_xacts;
 	List	   *relations;
 
@@ -153,9 +152,6 @@ vacuum(VacuumStmt *vacstmt, Oid relid, bool do_toast,
 	}
 	vac_strategy = bstrategy;
 
-	/* Remember whether we are processing everything in the DB */
-	all_rels = (!OidIsValid(relid) && vacstmt->relation == NULL);
-
 	/*
 	 * Build list of relations to process, unless caller gave us one. (If we
 	 * build one, we put it in vac_context for safekeeping.)