__futex(2): use outside Linux compat

[tlaronde%kergis.com@localhost]

In Mesa code implementations for futex_wake() and futex_wait() are
provided for Linux, Windows, FreeBSD and OpenBSD.

There is a __futex(2) syscall in NetBSD, used only for now, if I'm not
mistaken, to implement Linux compat.

Is it OK to use for NetBSD "native" code since it is not "advertised"
by a man page?
-- 
        Thierry Laronde <tlaronde +AT+ kergis +dot+ com>
                     http://www.kergis.com/
                    http://kertex.kergis.com/
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