standardize on 'int' for message sizes

that's what the sources already assumed anyway. size_t is total
overkill, as No Email Ever (TM) will exceed 2GiB.

this also fixes a harmless format string warning in 32 bit builds.

src/driver.h

@@ -39,7 +39,7 @@ typedef struct store_conf {
 	const char *flat_delim;
 	const char *map_inbox;
 	const char *trash;
-	uint max_size; /* off_t is overkill */
+	int max_size; /* off_t is overkill */
 	char trash_remote_new, trash_only_new;
 } store_conf_t;
 
@@ -64,7 +64,7 @@ typedef struct message {
 	struct message *next;
 	struct sync_rec *srec;
 	/* string_list_t *keywords; */
-	size_t size; /* zero implies "not fetched" */
+	int size; /* zero implies "not fetched" */
 	int uid;
 	uchar flags, status;
 	char tuid[TUIDL];

src/sync.c

@@ -1369,7 +1369,7 @@ box_loaded( int sts, void *aux )
 		uid = tmsg->uid;
 		if (DFlags & DEBUG_SYNC) {
 			make_flags( tmsg->flags, fbuf );
-			printf( svars->ctx[t]->opts & OPEN_SIZE ? "  message %5d, %-4s, %6lu: " : "  message %5d, %-4s: ", uid, fbuf, tmsg->size );
+			printf( svars->ctx[t]->opts & OPEN_SIZE ? "  message %5d, %-4s, %6d: " : "  message %5d, %-4s: ", uid, fbuf, tmsg->size );
 		}
 		idx = (uint)((uint)uid * 1103515245U) % hashsz;
 		while (srecmap[idx].uid) {