Fix a typo : pthread_mutexaddr_init -> pthread_mutexattr_init.

Fix some lint.

Too much or too little whitespace;
improve macro usage;
add missing .El;
merge error sections for same error code.

GSoC 2016 Charles Cui: Implement thread priority protection based on work
by Andy Doran. Also document the get/set pshared thread calls as not
implemented, and add a skeleton implementation that is d

GSoC 2016 Charles Cui: Implement thread priority protection based on work
by Andy Doran. Also document the get/set pshared thread calls as not
implemented, and add a skeleton implementation that is disabled.
XXX: document _sched_protect(2).

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.Xr instaed of .Fn for pthread_mutex_init(3), update the error codes,
cleanup STANDARDS, etc.

Use a list with the mutex type. Note, from the standard, that recursive
mutexes should be avoided when condition variables are used.

Avoid duplicate .Pp.

Move TNF licenses to 2 clause form

Fixed spelling error.

New sentence, new line.

Fix various spelling errors.

From Igor Sobrado in PR/29997.

Add restrict qualifiers to <pthread.h> function arguments.

Drop trailing whitespace.

$NetBSD$, not $Header$.

Man pages for libpthread, adapted from FreeBSD by Stephen Degler.