tls: check ciphersuite string validity early
tls: check ciphersuite string validity early

Author: jsing <jsing>
Date:   Wed Jul 6 16:47:18 2016 +0000

    Check that the given ciphers string is syntactically valid and results in
    at least one matching cipher suite.

    ok doug@

ifduyue/libusual,markokr/libusual,markokr/libusual,ifduyue/libusual,markokr/libusual,ifduyue/libusual,markokr/libusual,ifduyue/libusual