XSB Prolog added to wip

[Mayuresh <mayuresh%acm.org@localhost>]

Among Prologs, XSB Prolog has some unique features like deductive
database.

I have committed wip/xsb package. It would be great if someone can review.

In particular, I am unsure about this patch. PTHREAD_MUTEX_ERRORCHECK_NP
isn't available on NetBSD 9.x (may be it would come in 10). I just
replaced it with PTHREAD_MUTEX_ERRORCHECK, but not sure what is the right
patch for this.

    +#if defined(__NetBSD__)
    +#    define PTHREAD_MUTEX_ERRORCHECK_NP PTHREAD_MUTEX_ERRORCHECK
    +#endif

I'll submit all patches upstream, once someone reviews them here.

BTW about 11 years back I had attempted creating package for XSB and given
up back then![1]

[1] http://mail-index.netbsd.org/pkgsrc-users/2011/11/13/msg015344.html

-- 
Mayuresh