Bug 915408: Use SHA-1 in TLS 1.2 client auth if the server requests it.
Bug 915408: Use SHA-1 in TLS 1.2 client auth if the server requests it.

Consider the signature algorithms requested by the server in addition to those
supported by the client key in ssl3_DestroyBackupHandshakeHashIfNotNeeded.

r=wtc.

nmav/nss,nmav/nss,nmav/nss,ekr/nss-old,ekr/nss-old,ekr/nss-old,nmav/nss,ekr/nss-old,nmav/nss,ekr/nss-old,nmav/nss,nmav/nss,ekr/nss-old,ekr/nss-old