(current_column_1, Fmove_to_column):
Update call to CHAR_HEAD_P.
(indented_beyond_p): Take POS in bytes and chars. Callers changed.
(pos_tab_indent): Function moved to xdisp.c.
(Fcurrent_indentation): Use scan_newline and SET_PT_BOTH.
(indented_beyond_p, current_column_1): Likewise.
(vmotion, compute_motion): Set up bytepos value to return it.
(current_column): Handle bytepos and charpos.
(position_indentation): Take bytepos as arg, and scan with it. Calls changed.
(Fmove_to_column): Scan with bytepos and charpos.
(pos_tab_offset): Use bytepos to do FETCH_BYTE.
(skip_invisible): Don't worry about position in middle of character.