NX agent contains/ed two build trees. An old one (probably pre-3.x.y)
 and a "newer" one. The "newer" code tree used to become enabled by
 setting NXUpgradeAgentServer in nx-X11/config/cf/host.def to YES.

 As building the NXUpgradeAgentServer has been the default for
 years now, we drop all code that does not get used at build time
 for NXUpgradeAgentServer == YES (i.e., the code that belongs to the
 pre-3.x.y phase of NX agent).