By design, when resuming a session, Xinerama can only be re-enabled
 by NX option parsing.

 Thus, this change introduces a "xinerama" NX option that can
 be loaded via an options file into NX agent when resuming
 a session. The new xinerame NX session option also allows
 switching on Xinerama at session startup via an option file.

 When implementing the new NX Xinerama support into clients (like
 TheQVD, X2Go Client, etc., this new xinerama NX option should be
 used for activating Xinerama in the NX / QVD / X2Go session.