Hello @jer-gentoo, I just finished working on OpenSSL 1.1.0-pre5, so @dmiller-nmap explained me what was intended here, and asked me if I could merge your work. Thus, I am writing to you to tell you that I've just made the corresponding changes to check for EVP_PKEY_get1_EC_KEY() usability. This has been commited to the SVN trunk in revision 36069.
The modified files are:

M       configure
M       configure.ac
M       nmap_config.h.in
M       nse_ssl_cert.cc

To be short, I've used your configure.ac file as is, autoconf (updated) the configure file, changed HAVE_EVP_PKEY_EC to HAVE_OPENSSL_EC, and declared the latter in nmap_config.h.in.

Of course, your name is mentioned in the commit title.
Thanks for your contribution!
Cheers

Merged in r36069 (a2b5a1a)