Description of problem:
NSS 3.15.1+ supports TLSv1.2, mod_nss can enable it now as well. Support was added to NSS via BZ https://bugzilla.mozilla.org/show_bug.cgi?id=480514
The basic framework for supporting it in mod_nss is already there from BZ https://bugzilla.redhat.com/show_bug.cgi?id=979798
Included in new mod_nss 1.0.10 release.