Enable ECDSA signatures

(from rpm-5.3 development in 2010)
===================================
gnupg2 and libgcrypt needs to be recompiled +ECC.
    Announce is here
        http://www.gossamer-threads.com/lists/gnupg/devel/51762
    with code here
        http://code.google.com/p/gnupg-ecc/
    and IETF draft here
        http://sites.google.com/site/brainhub/pgp

nss-3.12.8 needs to be patched +ECDSA and recompiled.
    Packaged on RHEL6.

openssl 1.0.0a needs to be patched +ECDSA and recompiled.
    Packaged on RHEL6.

libtomcrypt needs to be packaged and recompiled.

(from rpm-5.4 development in August 2013)
===================================
ECDSA is passing internally consistent generate-sign-verify tests using
recompiled Fedora packages with these specific versions:
   libgcrypt-1.5.3-1.el6.x86_64 (after undoing RHEL6 removal)
   nss-3.15.1-3.el6.x86_64 (after undoing RHEL6 removal)
   openssl-1.0.1e-13.el6.x86_64 (after undoing RHEL6 removal
   libtomcrypt-1.17-18.el6.x86_64

Getting gnupg +ECDSA pubkeys which are then parsed/verified remains
to be tested. The original pre-RFC6637 format has been implemented, but oid -> curve
parameter lookup is surely going to need de facto examples/tests.

There are example RFC 6637 keys/signatures here:
    http://code.google.com/p/gnupg-ecc/