Be compliant with POS36-C: Observe correct revocation order while relinquishing privileges (602_nx-X11_initgroups.full.patch).

  The Fedora review of NX (redistributed) caught the following rpmlint issue:

  This executable is calling setuid and setgid without setgroups or initgroups.
  There is a high probability this mean it didn't relinquish all groups, and this
  would be a potential security issue to be fixed. Seek POS36-C on the web for
  details about the problem.

  Ref POS36-C:
  https://www.securecoding.cert.org/confluence/display/seccode/POS36-C.+Observe+correct+revocation+order+while+relinquishing+privileges

  This patch adds initgroups() calls to the code to initialize the supplemental group list.