Remove an incorrect assertion on move_it_by_lines.

src/xdisp.c (move_it_by_lines): Remove the assertion that
 "it->current_x == 0 && it->hpos == 0" which can be legitimately
 violated when there's a before-string at the beginning of a line.
 (Bug#11063)

src/ChangeLog

@@ -4,6 +4,10 @@
 	string comes from a `display' text property, use the buffer
 	position of that property as if we actually saw that position in
 	the row's glyphs.
+	(move_it_by_lines): Remove the assertion that
+	"it->current_x == 0 && it->hpos == 0" which can be legitimately
+	violated when there's a before-string at the beginning of a line.
+	(Bug#11063)
 
 2012-03-30  Eli Zaretskii  <eliz@gnu.org>
 

src/xdisp.c

@@ -8966,7 +8966,6 @@ move_it_by_lines (struct it *it, int dvpos)
     {
       /* DVPOS == 0 means move to the start of the screen line.  */
       move_it_vertically_backward (it, 0);
-      xassert (it->current_x == 0 && it->hpos == 0);
       /* Let next call to line_bottom_y calculate real line height */
       last_height = 0;
     }