Fix for too overall Xdamage and Xrandr client lib removal: Bring back the nx-x11proto-{randr,damage} header files and use those at compile time.

library clean-up: Don't build libNX_Xdamage anymore. Use system's libXdamage shared library. (Fixes ArcticaProject/nx-libs#6, X2GoBTS#826).

  * Debian/Ubuntu packaging:
    + Fully rework the way nx-libs gets packaged for Debian/Ubuntu.
    + Split up libnx-x11 into individual packages.
    + Provide dbg:packages for each bin:package containing binaries.
    + Use Makefile logic to install files into DESTDIR.
    + Provide dev:packages for each lib:package individually.
    + Provide nx-x11proto-*-dev packages for all libnx-* libraries.
    + Install _all_ library files (*.so*) to /usr/lib/<triplet>/, so
      no extra settings of LD_LIBRARY_PATH is necessary.