Fixes ArcticaProject/nx-libs#546.

Makefile: Align variable names USRLIBDIR, SHLIBDIR (and NX_DIR) with nx-X11 internal naming schemes (and use /usr/<lib>/nx/X11 rather than /usr/<lib>/nx-X11).

Makefile: Align variable names USRLIBDIR, SHLIBDIR (and NX_DIR) with nx-X11 internal naming schemes (and use /usr/<lib>/nx/X11 rather than /usr/<lib>/nx-X11).

  o Install nxagent/nxproxy executables into multi-arch path.
  o Fake libNX_X11.so* as $LIBDIR/nx-X11/libX11.so*.
  o Allow injecting different $NXAPP containing the executable name.

  o For e.g. x2goagent this requires the following changes:

    - Move x2goagent symlink from /usr/lib/x2go/bin/x2goagent to
      $LIBDIR/nx/bin/x2goagent
    - Replace /usr/bin/x2goagent by a two-liner...

    ```
    #!/bin/sh

    export NXAPP=x2goagent
    nxagent
    ```

 The x2goagent package is being replaced by an x2goserver bin:package
 named x2goserver-x2goagent.

 This x2goserver-x2goagent bin:package will be maintained in the X2Go
 Project's namespace and basically wraps around nxagent.

 Furthermore, declare Arctica Project as upstream source for nx-libs.

  * 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.

Provide a default keystrokes.cfg in /etc/nx (for nxagent) and /etc/x2go (for x2goagent). (Fixes: #199).

Drop patch 032, fix other patches so that installation via make install installs NX components to /usr/local/lib/nx and /usr/local/include/nx.

  - 005_add-nxagent-wrapper.patch.
  - 008_add-nxproxy-wrapper.patch.
  - 011_add-nxauth-wrapper.patch.

  - 101_nxagent_set-rgb-path.patch
  - 102_xserver-xext_set-securitypolicy-path.patch
  - 103_nxagent_set-X0-config-path.patch
  - 104_nxagent_enable_debug.patch
  - 105_nxagent_export-remote-keyboard-config.patch
  - 106_nxagent_utf8-copy-clipboard.patch
  - 107_nxagent_clipboard-compound-text+small-bed-sheets.patch
  - 108_nxagent_wine-close-delay.patch
  - 109_nxagent_locale-utf8-compound-text.patch
  - 200_nxagent_unbrand-agent.patch