(lwupdate): New function, mostly was __line_wrap_update. Use POINT_COL field...

(lwupdate):   New function, mostly was __line_wrap_update.   Use POINT_COL field instead of POINT.   Update D->point_offs when done.   Use memmove instead of memcpy where overlap is possible (not      necessary using current implementation of memcpy, but...). (__line_wrap_output): Use lwupdate. (__line_wrap_update): New function. (line_wrap_set_lmargin, line_wrap_set_rmargin,   line_wrap_set_wmargin, line_wrap_point): Use __line_wrap_update. (ensure_unwrapped, ensure_wrapped): New functions.