Tweak FOR UPDATE/SHARE error message wording (again)

In commit 0ac5ad5134 I changed some error messages from "FOR
UPDATE/SHARE" to a rather long gobbledygook which nobody liked.  Then,
in commit cb9b66d31 I changed them again, but the alternative chosen
there was deemed suboptimal by Peter Eisentraut, who in message
1373937980.20441.8.camel@vanquo.pezone.net proposed an alternative
involving a dynamically-constructed string based on the actual locking
strength specified in the SQL command.  This patch implements that
suggestion.

src/backend/optimizer/plan/initsplan.c

@@ -26,6 +26,7 @@
 #include "optimizer/prep.h"
 #include "optimizer/restrictinfo.h"
 #include "optimizer/var.h"
+#include "parser/analyze.h"
 #include "rewrite/rewriteManip.h"
 #include "utils/lsyscache.h"
 
@@ -883,7 +884,10 @@ make_outerjoininfo(PlannerInfo *root,
 			(jointype == JOIN_FULL && bms_is_member(rc->rti, left_rels)))
 			ereport(ERROR,
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("row-level locks cannot be applied to the nullable side of an outer join")));
+					 /*------
+					  translator: %s is a SQL row locking clause such as FOR UPDATE */
+					 errmsg("%s cannot be applied to the nullable side of an outer join",
+							LCS_asString(rc->strength))));
 	}
 
 	sjinfo->syn_lefthand = left_rels;

src/backend/optimizer/plan/planner.c

@@ -1081,7 +1081,11 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
 		if (parse->rowMarks)
 			ereport(ERROR,
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("row-level locks are not allowed with UNION/INTERSECT/EXCEPT")));
+					 /*------
+					   translator: %s is a SQL row locking clause such as FOR UPDATE */
+					 errmsg("%s is not allowed with UNION/INTERSECT/EXCEPT",
+							LCS_asString(((RowMarkClause *)
+										  linitial(parse->rowMarks))->strength))));
 
 		/*
 		 * Calculate pathkeys that represent result ordering requirements