PKCS12_create(3): remove Xr to EVP_PKEY_add1_attr(3)

This API family has been neutered and will be removed in the next bump.
Further cross references will be untangled in the future.

man pages: add missing commas between subordinate and main clauses

jmc@ dislikes a comma before "then" in a conditional, so leave those
untouched.

ok jmc@

new manual page EVP_PKEY_add1_attr(3) documenting nine functions
for associating X.501 Attributes with private keys

new manual page for X509_keyid_set1(3), X509_keyid_get0(3),
X509_alias_set1(3), X509_alias_get0(3)

add links back to crypto(3) to function group entry pages
and to isolated obsolete pages;
OK bcook@ jmc@

Tree structure for manual pages: crypto(3) links to 33 function
group pages, and these link on to all their second-level subpages.
Only a handful of second-level pages have third-level subpages.
So a

Tree structure for manual pages: crypto(3) links to 33 function
group pages, and these link on to all their second-level subpages.
Only a handful of second-level pages have third-level subpages.
So all crypto pages can now be reached from the www.libressl.org
frontpage via at most four clicks, in most cases three clicks.
Also link back from leaf pages to their respective group pages
and add a couple of additional links between related pages.
Triggered by a question from deraadt@.
OK jmc@ tb@

show more ...

In pkcs12.h rev. 1.18 2018/05/13 13:46:55, tb@ added const qualifiers
to the "pass" and "name" arguments of PKCS12_create(3). Adjust the manual.

crypto HISTORY up to 0.9.3; researched from OpenSSL git

Add missing RETURN VALUES section;
from Paul Yang via OpenSSL commit 1f13ad31 Dec 25 17:50:39 2017 +0800.

Copyright and license

various cleanup; leaving dangling PKCS7* Xr for now...

first pass; ok schwarze

convert PEM and PKCS manuals from pod to mdoc