Redesign bidi-aware edge positions of glyph rows, fix bug #6036.

Redesign bidi-aware edge positions of glyph rows, fix bug #6036.

 dispextern.h (struct glyph_row): New members minpos and maxpos.
 (MATRIX_ROW_START_CHARPOS, MATRIX_ROW_START_BYTEPOS)
 (MATRIX_ROW_END_CHARPOS, MATRIX_ROW_END_BYTEPOS): Reference minpos
 and maxpos members instead of start.pos and end.pos, respectively.
 xdisp.c (display_line): Compare IT_CHARPOS with the position in
 row->start.pos, rather than with MATRIX_ROW_START_CHARPOS.
 (cursor_row_p): Use row->end.pos rather than MATRIX_ROW_END_CHARPOS.
 (try_window_reusing_current_matrix, try_window_id): Use
 ROW->minpos rather than ROW->start.pos.
 (init_from_display_pos, init_iterator): Use EMACS_INT for
 character and byte positions.
 (find_row_edges): Renamed from find_row_end.  Accept additional
 arguments for minimum and maximum buffer positions seen by
 display_line for this row.  Don't use iterator to find the
 position following the maximum one; instead, increment the
 position found by display_line directly.  Fix logic; eol_pos
 should be tested before the rest.  Handle the case of characters
 delivered from display vector (bug#6036).  Fix tests related to
 it->method.  Handle the truncated_on_right_p rows.
 (RECORD_MAX_MIN_POS): New macro.
 (display_line): Use it to record the minimum and maximum buffer
 positions for glyphs in the row being assembled.  Record the
 position of the newline that terminates the line.  If word wrap is
 in effect, restore minimum and maximum positions seen up to the
 wrap point, when iterator returns to it.
 (try_window_reusing_current_matrix): Give up if in bidi-reordered
 row and cursor not already at point.  Restore original pre-bidi
 code for unidirectional buffers.
 dispnew.c (increment_row_positions, check_matrix_invariants):
 Increment and check row->start.pos and row->end.pos, in addition
 to MATRIX_ROW_START_CHARPOS and MATRIX_ROW_END_CHARPOS.
 .gdbinit (prowlims): Display row->minpos and row->maxpos.
 Display truncated_on_left_p and truncated_on_right_p flags.
 Formatting fixes.
 (pmtxrows): Display the ordinal number of each row.  Don't display
 rows beyond the last one.
 bidi.c (bidi_cache_iterator_state): Don't zero out new_paragraph:
 it is not copied by bidi_copy_it.