Fix format string for off_t.

--- gimgch.c.orig	Sun Mar 10 22:24:39 2013
+++ gimgch.c	Sun Mar 10 22:24:46 2013
@@ -47,7 +47,7 @@ static void display_headers (int line_columns)
 	emptyid[strlen(headers[0]->id)] = '\0';
 
 	for (i = 0; i < header_num; i ++) {
-		printf("%s %8x=foff %8x=flen %4x=hoff %4x=hlen %s %s\n",
+		printf("%s %8llx=foff %8x=flen %4x=hoff %4x=hlen %s %s\n",
 				headers[i]->id,
 				headers[i]->subfile_offset,
 				headers[i]->subfile_size,
