The saml:sp:IdP authentication data was only saved for SAML 2.0
authentication. This patch moves this variable into common code, so
that it is shared between SAML 2.0 and SAML 1.1.

Thanks to Tim Jobling for reporting this bug!

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@3240 44740490-163a-0410-bde0-09ae8108e29a