use system libXext instead

Attributes GH PR #152: https://github.com/ArcticaProject/nx-libs/pull/152
Reviewed by: Vadim Troshchinskiy <vadim@qindel.com>  -- Fri, 01 Jul 2016 14:55:00 +0200

Attributes GH PR: https://github.com/ArcticaProject/nx-libs/pull/151
Self-reviewed: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>  -- Fri, 01 Jul 2016 14:03:44 +0200

debian/*.dirs: Don't create directories in the Debian package. All handled well by the upstream Makefile.

 ... detected by Debian's lintian tool.

debian/control: Drop various not-used-anymore libNX_* related packages. Add B:/R: to libnx-x11-{6,dev,6-dbg) to uninstall those package when upgrading to nx-libs 3.6.x.

roll-tarball.sh: Don't ship doc/X11-symbols/ in the lite (proxy-only) tarball derived from the nx-libs code tree.

debian/rules: Don't attempt at removing $(CURDIR)/.preserve/. Not needed anymore since we removed the CODE-REDUCTION_* hacks from debian/rules.

Attributes GH PR #150: https://github.com/ArcticaProject/nx-libs/pull/150
Reviewed by: Vadim Troshchinskiy <vadim@qindel.com>  -- Fri, 01 Jul 2016 04:33:22 -0700

 Note: This breaks building on ancient Linux distro versions, e.g. Ubuntu
 10.04 LTS.

 For details see:
 http://man7.org/tlpi/code/faq.html#use_default_source

Attributes GH PR #148: https://github.com/ArcticaProject/nx-libs/pull/148
Reviewed by Vadim Troshchinskiy <vadim@qindel.com>  -- Fri, 01 Jul 2016 03:12:26 -0700

Attributes GH PR #149: https://github.com/ArcticaProject/nx-libs/pull/149
Reviewed by Vadim Troshchinskiy <vadim@qindel.com>  -- Fri, 01 Jul 2016 02:02:49 -0700

 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

debian/libnx-x11-6.symbols: Update symbols (added: _XEatDataWords@Base 3.5.99.0, _XGetRequest@Base 3.5.99.0).

Attributes GH PR #146: https://github.com/ArcticaProject/nx-libs/pull/146
Reviewed by: Vadim Troshchinskiy <vadim@qindel.com>  -- Thu, 30 Jun 2016 06:30:46 -0700

Attributes GH PR #170: https://github.com/ArcticaProject/nx-libs/pull/170

This required for successful linking of libXrender against libNX_X11.

Port from libXfixes commit b031e3b60fa1af9e49449f23d4a84395868be3ab We
need this here to enable linking of current libXrender against
libNX_X11 instead of the system's libX11

The original implementation of this function (libX11 commit
9f5d83706543696fc944c1835a403938c06f2cc5) uses xcb stuff which we do
not have in libNX_X11. So we take a workaround from another lib. This
workaround had been added temporarily to a couple of X extension libs,
see
e.g. https://lists.x.org/archives/xorg-devel/2013-July/036763.html.

To enable linking of a current libXrender libNX_X11 needs that symbol.

This is a (manual) backport of the following upstream libX11 commit
available at
https://cgit.freedesktop.org/xorg/lib/libX11/commit/src/XlibInt.c?id=4a060f993bf676cf21ad9784e010f54134da7b40:

     Commit: 4a060f993bf676cf21ad9784e010f54134da7b40
     Author: Peter Hutterer <peter.hutterer@who-t.net>
     Date: Mon, 17 Oct 2011 09:45:15 +1000
     Subject: Add _XGetRequest as substitute for GetReq/GetReqExtra

Attributes GH PR #145: https://github.com/ArcticaProject/nx-libs/pull/145
Self-reviewed: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>  -- Wed, 29 Jun 2016 11:22:30 +0200

 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.

Attributes GH PR #121: https://github.com/ArcticaProject/nx-libs/pull/121
Reviewed by: Vadim Troshchinskiy <vadim@qindel.com>  -- Wed, 29 Jun 2016 00:45:43 -0700