Make nxproxy and nxagent print an arbitrary version number by running
make NX_VERSION_CUSTOM="myvers". nxagent and nxproxy will then show
this in addition to the original version number:

NXPROXY - Version myvers (3.5.99.22)
NXAGENT - Version myvers (3.5.99.22)

Fixes ArcticaProject/nx-libs#606

Attributes GH PR #883: https://github.com/ArcticaProject/nx-libs/pull/883

XlibAtom should be used wherever remote atoms are handled. This is
important as Xlib data types and server data types of the same name do
not always have identical sizes.

See also https://lists.freedesktop.org/archives/xorg-devel/2015-August/047245.html

Attributes GH PR #869: https://github.com/ArcticaProject/nx-libs/pull/869