Improve tab whitespace in file.

Add comment about $$ and '' SCONST strings.

src/interfaces/ecpg/preproc/preproc.y

-/* $PostgreSQL: pgsql/src/interfaces/ecpg/preproc/preproc.y,v 1.317 2006/02/01 22:16:36 momjian Exp $ */
+/* $PostgreSQL: pgsql/src/interfaces/ecpg/preproc/preproc.y,v 1.318 2006/02/03 05:38:35 momjian Exp $ */
 
 /* Copyright comment */
 %{
@@ -4375,11 +4375,12 @@ Bconst:  BCONST				{ $$ = make_name();};
 Xconst:  XCONST				{ $$ = make_name();};
 Sconst:  SCONST
 		{
+			/* could have been input as '' or $$ */
 			$$ = (char *)mm_alloc(strlen($1) + 3);
 			$$[0]='\'';
 			strcpy($$+1, $1);
-			$$[strlen($1)+2]='\0';
 			$$[strlen($1)+1]='\'';
+			$$[strlen($1)+2]='\0';
 			free($1);
 		}
 		;