Remove support for linking with libeay32 and ssleay32

Remove support for linking with libeay32 and ssleay32

The OpenSSL project stopped using the eay names back in 2016
on platforms other than Microsoft Windows, and version 1.1.0
removed the names from Windows as well. Since we now require
OpenSSL 1.1.1 we can remove support for using the eay names
from our tree as well.

Author: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/3C445F8E-D43E-4970-9CD9-A54882197714@yesql.se
Discussion: https://postgr.es/m/CAHrt6656W9OnFomQTHBGYDcM5CKZ7hcgzFt8L+N0ezBZfcN3zA@mail.gmail.com