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.
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