Fixes ArcticaProject/nx-libs#546.

Works around libtool bug related to using both -nostdlib and -pthread
(with the former dropping latter usage.)

nx{comp{,shad},proxy}: add configure flag --enable-cxx11 to enable and setup optional C++11 support.

Use AX_CXX_COMPILE_STDCXX(_11) from autotools archive.

Note: should only be used in tandem. Make sure that each component
either uses the C++11 ABI or none uses it. Mixing and matching libraries
and binaries with different C++ ABIs might lead to weird errors.

 Fixes ArcticaProject/nx-libs#506.

nxproxy/src/Makefile.am: Actually define nxproxy_CFLAGS, so the various compiler warning flags get enabled at build time of nxproxy.

nxproxy/configure.ac: Have AC_LANG before NX_COMPILER_BRAND. Thanks to Ionic for spotting this same flaw in nxcompshad.

 This also solves the last remnant of overlinking as described in GH issue #133.

 Fixes ArcticaProject/nx-libs#133.

 Fixes ArcticaProject/nx-libs#98.

 Drop other LICENSE files added by NoMachine scattered all over the code tree.

 One COPYING file in the project's base folder is sufficient.

 Note:

  - The "normal" way to inject CFLAGS (and CPPFLAGS) into nx-X11 builds is copying those
    options over into the variable CDEBUGFLAGS.
  - LDFLAGS have to be handed to nx-X11 via LOCAL_LDFLAGS.

 This change also includes a slight change in the nx-X11 build order.

 Old build order:

  Main Makefile:

      - [...]
      - libNX_X11
        + implicitly building nxcomp
        + implicitly building nxcompext
      - [...]
      - nxagent
        + implicitly building nxcompshad
      - [...]

 New build ordner:

  Main Makefile:

      - [...]
      - nxcomp
      - setup nx-X11 build env
        + cd nx-X11 && make BuildEnv
      - nx-X11/lib/*
      - nxcompext
      - nxcompshad
      - [...]
      - nxagent
      - [...]

 Fixes ArcticaProject/nx-libs#141
 Fixes X2GoBTS#84

 Note:

  - The "normal" way to inject CFLAGS (and CPPFLAGS) into nx-X11 builds is copying those
    options over into the variable CDEBUGFLAGS.
  - LDFLAGS have to be handed to nx-X11 via LOCAL_LDFLAGS.

 This change also includes a slight change in the nx-X11 build order.

 Old build order:

  Main Makefile:

      - [...]
      - libNX_X11
        + implicitly building nxcomp
        + implicitly building nxcompext
      - [...]
      - nxagent
        + implicitly building nxcompshad
      - [...]

 New build ordner:

  Main Makefile:

      - [...]
      - nxcomp
      - setup nx-X11 build env
        + cd nx-X11 && make BuildEnv
      - nxcompext
      - nxcompshad
      - nx-X11/lib/*
      - [...]
      - nxagent
      - [...]

 Fixes ArcticaProject/nx-libs#141
 Fixes X2GoBTS#84

xorg-server does not follow the convention of using 2 dashes,
and apparently nx-libs doesn't either.

Note that --help does produce the help output. However, it
produces this additional output after it:

Error: NX transport initialization failed.

Therefore, we should instruct users to call -help instead.

xorg-server does not follow the convention of using 2 dashes,
and apparently nx-libs doesn't either.

Note that --help does produce the help output. However, it
produces this additional output after it:

Error: NX transport initialization failed.

Therefore, we should instruct users to call -help instead.

VERSION file: master VERSION file is in base folder, symlinked from nx*/VERSION and hw/nxagent/VERSION.

  This commit removes the debian/VERSION file at makes it now unnecessary to
  copy/symlink the VERSION file at build time. These build scripts got adapted:

    debian/roll-tarballs.sh
    debian/rules
    nx-libs.spec

  Furthermore, all NX component now use the main VERSION file as reference.

    typechange: nxcomp/VERSION
    typechange: nxcompext/VERSION
    typechange: nxcompshad/VERSION
    typechange: nxproxy/VERSION

 026_nxcompext_honour-optflags.full.patch
 026_nxcomp_honour-optflags.full+lite.patch
 026_nxcompshad_honour-optflags.full.patch

  024_fix-make-clean.full.patch
  024_fix-make-clean.full+lite.patch

  009_nxproxy_add-man-page.full+lite.patch
  009_nxagent_add-man-page.full.patch
  010_nxauth_fix-binary-name-in-man-page.full.patch

This reverts commit e77bf36d.