BIO_s_bio.pod.  The most logical is to move everything needed from
BIO_new_bio_pair.pod to BIO_s_bio.pod (including the nice example)
and toss BIO_new_bio_pair.pod.  I hope I got all the info over properly.
PR: 370

(it's similar to the shutdown(..., SHUT_WR) system call
for sockets).

Update docs.

which is redundant.  They are now in their own document.

Also, in the name section, all the functions described shoud be
enumerated.  This will also make it much simpler to generate softlinks
name like each function to man-pages containing the info.

This combines several manual pages provided by
Lutz Jaenicke <Lutz.Jaenicke@aet.TU-Cottbus.DE>,
various comments by Bodo to the lists and a bit
of source examination by me.