curses: clarify standout as the "best" _supported_ highlighting mode
of the current terminal

curses: clarify documentation regarding the standout attribute

The BUGS sections is incorrect again for "modern" terminals.

For example, wscons and xterm both display standout differently to bold.

PR/51673: Carsten Kunze: curses: standend() does not turn off A_BOLD;
according the X/Open it needs to turn off all attributes.

re-work the previous to make it format correctly

document the correct argument to wstandout(3) and wstandend(3)

Convert TNF licenses to new 2 clause variant

Use
.In header.h
instead of
.Fd #include \*[Lt]header.h\*[Gt]
Much easier to read and write, and supported by groff for ages.
Okayed by ross.

Drop trailing whitespace.

Added separate man pages for curses functions to provide better
documentation of the curses functions.