Fix a dozen or so places that were passing unpredictable data strings

as elog format strings.  Hai-Chen Tu pointed out the problem in
contrib/dbmirror, but it wasn't the only such error.

contrib/cube/cubeparse.y

@@ -200,7 +200,7 @@ int cube_yyerror ( char *msg ) {
 	  );
 
   reset_parse_buffer();     
-  elog(ERROR, buf);
+  elog(ERROR, "%s", buf);
   return 0;
 }