progress meter: fix bugs found in stall detection and unknown size logic

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/libbb.h b/include/libbb.h
index 7581cd4..65c3194 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1584,8 +1584,9 @@
 int print_flags(const masks_labels_t *ml, int flags) FAST_FUNC;
 
 typedef struct bb_progress_t {
-	off_t lastsize;
-	unsigned lastupdate_sec;
+	unsigned last_size;
+	unsigned last_update_sec;
+	unsigned last_change_sec;
 	unsigned start_sec;
 	const char *curfile;
 } bb_progress_t;