Add missing function names in the NAME section for rest of the man pages in libpthread

Bump date for previous.
New sentence, new line.

Make PTHREAD_KEYS_MAX dynamically adjustable

NetBSD's PTHREAD_KEYS_MAX is set to 256, which is low compared to
other systems like Linux (1024) or MacOS X (512). As a result some
setups tested on Lin

Make PTHREAD_KEYS_MAX dynamically adjustable

NetBSD's PTHREAD_KEYS_MAX is set to 256, which is low compared to
other systems like Linux (1024) or MacOS X (512). As a result some
setups tested on Linux will exhibit problems on NetBSD because of
pthread_keys usage beyond the limit. This happens for instance on
Apache with various module loaded, and in this case no particular
developper can be blamed for going beyond the limit, since several
modules from different sources contribute to the problem.

This patch makes the limit conigurable through the PTHREAD_KEYS_MAX
environement variable. If undefined, the default remains unchanged
(256). In any case, the value cannot be lowered below POSIX-mandated
_POSIX_THREAD_KEYS_MAX (128).

While there:
- use EXIT_FAILURE instead of 1 when calling err(3) in libpthread.
- Reset _POSIX_THREAD_KEYS_MAX to POSIX mandated 128, instead of 256.

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Mark up NULL.

Rationalize by moving

pthread_key_delete(3) to pthread_key_create(3); and
pthread_setspecific(3) to pthread_getspecific(3)

Move TNF licenses to 2 clause form

Mark up a defined value.

$NetBSD$, not $Header$.

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