copywin() couldn't seem to decide whether it should work in window or
screen coordinates - and managed to do neither.
Change copywin() to use window relative coords (as ncurses and solaris do),
and change overwrite() and overlay() to use the modified interface.
It is now possible to use overwrite() to save part of curscr while a
temporary window is drawn.
Fixes PR/26506
* Added code to __restartwin to restore meta and cursor visibility states
* Added code to __stopwin to disable meta.
* Added the *line group of functions for drawing character lines.
* Changed call to wrefresh in wgetch to be before input read.
* Changed default old cursor mode to be high vis in curs_set
* Added documentation for various new functions to fns.doc.
* Added function derwin.
* Added function copywin.
* Modified both overlay and overwrite to use copywin.
* Updated man page with new functions and fixed minor format glitch.
