phpdoc: Add missing @throws to a couple of methods in SimpleSAML_Session.
phpdoc: Add missing @throws to a couple of methods in SimpleSAML_Session.

simplesamlphp/simplesamlphp,dnmvisser/simplesamlphp,jschlyter/simplesamlphp,simplesamlphp/simplesamlphp,jschlyter/simplesamlphp,jschlyter/simplesamlphp,simplesamlphp/simplesamlphp,ghalse/simplesamlphp,ghalse/simplesamlphp,dnmvisser/simplesamlphp,sitya/simplesamlphp,dnmvisser/simplesamlphp,sitya/simplesamlphp,sitya/simplesamlphp,jschlyter/simplesamlphp,ghalse/simplesamlphp,jschlyter/simplesamlphp,sitya/simplesamlphp,dnmvisser/simplesamlphp,simplesamlphp/simplesamlphp,ghalse/simplesamlphp