Fix mouse highlight in bidi-reordered continued lines.

Fix mouse highlight in bidi-reordered continued lines.

 xdisp.c (row_containing_pos): Don't return too early when CHARPOS is in a
 bidi-reordered continued line.  Return immediately when the first
 hit is found in a line that is not continued, or when an exact
 match for CHARPOS is found.
 (mouse_face_from_buffer_pos): Rewrite to not assume that
 START_CHARPOS is always in mouse_face_beg_row.  If necessary, swap
 mouse_face_beg_row and mouse_face_end_row so that the former is
 always above the latter or identical to it.

 Continued lines that begin or end outside of the visible region
 still don't work.