[patch v1] manual: add more pthread functions

[Collin Funk]

DJ Delorie <dj@redhat.com> writes:

> Add stubs and partial docs for many undocumented pthreads functions.
> While neither exhaustive nor complete, gives minimal usage docs
> for many functions and expands the pthreads chapters, making it
> easier to continue improving this section in the future.

These look good to me. I notice some missing @standards{...}, but as you
mention those can be added when they are more than just stubs.

Two lines have a trailing space though:

> +* Creating and Destroying Threads:: 

and:

> +Like @code{pthread_spin_unlock} but returns 0 if the lock was unlocked, or EBUSY if 

Other than that, looks good.

Reviewed-by: Collin Funk <collin.funk1@gmail.com>

Collin