Reviewed-by: NRichard Levitte <levitte@openssl.org>

RT1556: doc/crypto/threads.pod
RT2024: Missing pages mentioned in crypto.pod
RT2890: Wrong size in ERR_string_error description.
RT3461: Better description of PEM Encryption
        (Jeffrey Walton <noloader@gmail.com>)
        Also, fix up formatting and removed some code examples
        that encourage unsafe patterns, like unencrypted private
        keys (Rich Salz)
RT4240: Document some speed flags (Tomas Mraz <tmraz@redhat.com>)
RT4260: Fix return value doc for X509_REQ_sign and X509_sign
        (Laetitia Baudoin <lbaudoin@google.com>)
Reviewed-by: NEmilia Käsper <emilia@openssl.org>

Make all mention of digest algorithm use "any supported algorithm"

RT2071, some new manpages from Victor B. Wagner <vitus@cryptocom.ru>:
    X509_LOOKUP_hash_dir.pod
    X509_check_ca.pod
    X509_check_issued.pod

RT 1600:
    Remove references to non-existant objects(3)
    Add RETURN VALUES to BIO_do_accept page.

RT1818:
    RSA_sign Can return values other than 0 on failure.

RT3634:
    Fix AES CBC aliases (Steffen Nurpmeso <sdaoden@yandex.com>)

RT3678:
    Some clarifications to BIO_new_pair
    (Devchandra L Meetei <dlmeetei@gmail.com>)

RT3787:
    Fix some EVP_ function return values
    (Laetitia Baudoin <lbaudoin@google.com>)
Reviewed-by: NTim Hudson <tjh@openssl.org>

Came up on the mailing list, from Ken Goldman.
Reviewed-by: NTim Hudson <tjh@openssl.org>

L<foo|foo> is sub-optimal  If the xref is the same as the title,
which is what we do, then you only need L<foo>.  This fixes all
1457 occurrences in 349 files.  Approximately.  (And pod used to
need both.)
Reviewed-by: NRichard Levitte <levitte@openssl.org>

PR#3071

The primary changes made are:
- Updates to the "NAME" section of many pages to correctly reflect the
functions defined on those pages. This section is automatically parsed
by the util/extract-names.pl script, so if it is not correct then
running "man" will not correctly locate the right manual pages.
- Updates to take account of where functions are now deprecated
- Full documentation of the ec sub-library
- A number of other typo corrections and other minor tweaks

MD4 implemented.  Assar Westerlund provided the digest code itself and the test utility, I added the bits to get a EVP interface, the command line utility and the speed test