Fix a typo that caused crashes in redisplay.

 src/xdisp.c (compute_stop_pos_backwards): Fix a typo that caused crashes while
 scrolling through multibyte text.

src/ChangeLog

@@ -5,6 +5,8 @@
 	that fails, clear the desired glyph matrix before returning a
 	failure indication to the caller.  Fixes leaving garbled display
 	when fast scrolling with a down-key.  (Bug#12403)
+	(compute_stop_pos_backwards): Fix a typo that caused crashes while
+	scrolling through multibyte text.
 
 2012-09-12  Jan Djärv  <jan.h.d@swipnet.se>
 

src/xdisp.c

@@ -7669,7 +7669,7 @@ compute_stop_pos_backwards (struct it *it)
     {
       it->end_charpos = min (charpos + 1, ZV);
       charpos = max (charpos - SCAN_BACK_LIMIT, BEGV);
-      SET_TEXT_POS (pos, charpos, BYTE_TO_CHAR (charpos));
+      SET_TEXT_POS (pos, charpos, CHAR_TO_BYTE (charpos));
       reseat_1 (it, pos, 0);
       compute_stop_pos (it);
       /* We must advance forward, right?  */