Properly define pg_upgrade global variable, per bug report from Chris

Ruprecht on Mac (64 bit).

contrib/pg_upgrade/pg_upgrade.h

@@ -237,7 +237,7 @@ typedef struct
 /*
  * Global variables
  */
-char		scandir_file_pattern[MAXPGPATH];
+extern char		scandir_file_pattern[];
 
 
 /* check.c */

contrib/pg_upgrade/relfilenode.c

@@ -17,6 +17,9 @@ static void transfer_relfile(migratorContext *ctx, pageCnvCtx *pageConverter,
 				 const char *oldnspname, const char *oldrelname,
 				 const char *newnspname, const char *newrelname);
 
+/* used by scandir(), must be global */
+char     scandir_file_pattern[MAXPGPATH];
+				 
 /*
  * transfer_all_new_dbs()
  *