RFR 8171277: Elliptic Curves for Security in Crypto

[Adam Petcher]

Webrev: http://cr.openjdk.java.net/~apetcher/8171277/webrev.00/
JBS: https://bugs.openjdk.java.net/browse/JDK-8171277

Please review this change that adds key agreement via the X25519 and 
X448 elliptic curve functions to the JCA API and SunEC provider. These 
functions and related operations and encodings are described in RFC 
7748[1]. This work does not include JSSE integration, which will be done 
later as a separate task (not part of JEP 324). The webrev does not 
include the field arithmetic code, which is being reviewed 
separately[2]. This change is a part of JEP 324, so it will not be 
integrated into the repo until all work for that JEP is complete and it 
has been targeted to a release.


[1] https://tools.ietf.org/html/rfc7748
[2] 
http://mail.openjdk.java.net/pipermail/security-dev/2018-January/016756.html