New NID for acmeIdentifier

[Angus Robertson - Magenta Systems Ltd]

Is it possible for a new NID and object to be added to support creating
and checking the Let's Encrypt ACME TLS-ALPN-01 challenge in which a
temporary X509 certificate is created with a specific X509v3 extension
containing shared information.

Currently, I get a new NID with: 

OBJ_create('1.3.6.1.5.5.7.1.31','acmeIdentifier','X509v3 ACME
Identifier')

Angus