- update to 3.15.1
* TLS 1.2 (RFC 5246) is supported. HMAC-SHA256 cipher suites
(RFC 5246 and RFC 5289) are supported, allowing TLS to be used
without MD5 and SHA-1.
Note the following limitations:
The hash function used in the signature for TLS 1.2 client
authentication must be the hash function of the TLS 1.2 PRF,
which is always SHA-256 in NSS 3.15.1.
AES GCM cipher suites are not yet supported.
* some bugfixes and improvements

- require libnssckbi instead of mozilla-nss-certs so p11-kit can
conflict with the latter (fate#314991)