in termios.h, but it's prototype in termcap.h and the main file use
the underlying definition (which is now an int, not a long for
compatibility with NetBSD). Really termcap.h should use speed_t too,
but I guess that this might break sources that don't include termios.h
first.
Basically all termios+termcap pgms needs it.
It set ospeed variable using nearest-matched stty speeds,
which helps termcap pgms works with non-fixed termios speeds
and not duplicate ospeed switch into every pgm.
Also it isn't standard function, its source code is too big to include it
in whole to every termcap+termios pgm.
