(display_line): Set row's and iterator's

(display_line): Set row's and iterator's
starts_in_middle_of_char_p and ends_in_middle_of_char_p flags.
Set cursor even if row ends in the middle of a character.
(dump_glyph_row): Print values of new flags.
(redisplay_window) <cursor movement in unchanged window>: When
point has been moved forward, and PT is at the end of the cursor
row, don't place the cursor in the next row if the cursor row ends
in the middle of a character or at ZV.