progress bar: better overflow protection; more precise bar

function                                             old     new   delta
bb_progress_update                                   639     749    +110

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/libbb.h b/include/libbb.h
index d390e68..c017880 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1592,8 +1592,9 @@
 
 void bb_progress_init(bb_progress_t *p) FAST_FUNC;
 void bb_progress_update(bb_progress_t *p, const char *curfile,
-			off_t beg_range, off_t transferred,
-			off_t totalsize) FAST_FUNC;
+			uoff_t beg_range,
+			uoff_t transferred,
+			uoff_t totalsize) FAST_FUNC;
 
 extern const char *applet_name;