Add curses ACS line graphics support for iso15 fonts

Add curses ACS line graphics support for iso15 fonts
Now ncurses-based programs such as sysinstall and mc will display the
correct font for graphical lines instead of "-" and "+" characters.

Correct two special characters for cons25l1 in termcap: use real
arrows instead of ">>" and "<<".
Add a lot of additional symbols for line drawing which are taken from
the CP437 font.
Almost all of the ACS symbols are now implemented.

PR: conf/90082
Submitted by: Oliver Fromme <olli@secnetix.de>
MFC after:	1 week