saml2_Message: Set AuthnInstant in assertion.
saml2_Message: Set AuthnInstant in assertion.

Fixes issue 225.
tectronics/simplesamlphp,vivekrajenderan/simplesamlphp,tectronics/simplesamlphp,tectronics/simplesamlphp,tectronics/simplesamlphp,tectronics/simplesamlphp,vivekrajenderan/simplesamlphp,vivekrajenderan/simplesamlphp,vivekrajenderan/simplesamlphp,vivekrajenderan/simplesamlphp