Use SSL_export_keying_material() if possible, i.e., if OpenSSL is
version 1.0.1 or newer and if client random value is used first. This
allows MSK derivation with TLS-based EAP methods (apart from EAP-FAST)
without exporting the master key from OpenSSL.
Signed-hostap: Jouni Malinen <j@w1.fi>