This fixes ArcticaProject/nx-libs#206.

nx-X11: Enable -Wpedantic as default CFLAG. This is to detect redefined typedefs when building nxagent.

Upstream does not use xkbfile but has own copies of the required
files. It was not used elsewhere.

 This has already been started while replacing copyright info in file
 headers and has now been completed with this commit.

Per-file copyright notices: Update copyright information in file headers that NoMachine placed there own copyright statement in.

  - Update XErrorDB to latest X.org version.
  - Install XErrorDB, XKeysymDB and Xcms.txt to /usr/{local/}share/nx/.
  - Assure that libNX_X11 finds those files at the
    named location.
  - Update debian/ packaging files.
  - Update nx-libs.spec packaging file.

Fixes ArcticaProject/nx-libs#153

 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

nx-X11/config/cf/lnxLib.tmpl requires post-library removal cleanup: Drop references to dropped X11 extension client libraries.

Fixes ArcticaProject/nx-libs#115.

  include/extensions: Xag.h, Xagsrv.h, Xagstr.h
  Xserver/Xext: appgroup.c, appgroup.h
  lib/Xext: XAppgroup.c

  include/extensions: Xcup.h, Xcupstr.h,
  Xserver/Xext: cup.c
  lib/Xext: cup.c

  include/extensions: Xdbe.h
  Xserver/Xext: Xdbe.c

  Xserver/Xext:  dgaproc.h, xf86dga.c, xf86dga2.c, xf86dgaext.h

  include/extensions: Xevie.h, Xeviestr.h
  include/extensions: XEVI.h, XEVIstr.h
  Xserver/Xext: EVI.c, EVIstruct.h, sampleEVI.c
  lib/Xext: XEVI.c

  include/extensions: fontcache.h, fontcacheP.h, fontcachstr.h
  Xserver/Xext: fontcache.c

  include/extensions: lbxbuf.h, lbxbufstr.h, lbxdeltastr.h, lbximage.h, lbxopts.h, lbxstr.h, lbxzlib.h
  lib/Xext: XLbx.c

  include/extensions: multibuf.h, multibufst.h
  lib/Xext: XMultibuf.c
  Xserver/Xext: mbuf.c, mbufbf.c, mbufpx.c

  include/extensions: xf86vmode.h, xf86vmstr.h
  Xserver/Xext: vidmodeproc.h, xf86vmode.c

  lib/Xext: MITMisc.c
  Xserver/Xext: mitmisc.c

  Xserver/Xext: xf86misc.c, xf86miscproc.h

  Xserver/XTrap: xf86XTrapModule.c, xtrapddmi.c, xtrapdi.c, xtrapdiswp.c, xtrapditbl.c
  include/extensions: xtrapbits.h xtrapddmi.h xtrapdi.h xtrapemacros.h xtraplib.h xtraplibp.h xtrapproto.h
  Fixes: ArcticaProject/nx-libs#116
  X.org: https://cgit.freedesktop.org/xorg/xserver/commit/?id=cbc20d92de92aad5ca240310a9156ccf97c24a01

  Plus: Drop various Imake'ish defines where not needed anymore.

library clean-up: Don't build libNX_Xinerama anymore. Use system's libXinerama shared library. (Fixes ArcticaProject/nx-libs#49).

 This commit goes along with a patch from Ulrich Sibiller who managed to
 move the Xinerama awareness for NX sessions into the Xserver code. This
 makes Xinerama support for NX in libNX_Xinerama.so obsolete.

 Fixes ArcticaProject/nx-libs#49

library clean-up: Don't build libNX_Xtst anymore. Use system's libXtst shared library. (Fixes ArcticaProject/nx-libs#32).

 In the process of building nxagent against more and more system-wide installed
 X.org libraries, we come to the limit of including structs from this (bundled
 nx-X11) and that (system-wide X.Org) library.

 This commit introduces a clear namespace separation of headers provided by
 nx-X11 and headers provided by X.Org. This approach is only temporary as we
 want to drop all nx-X11 bundled libraries from nx-libs.

 However, for a while we need to make this separation clear and also ship
 some reduced fake X.Org headers that avoid pulling in libX* and libNX_X*
 symbols at the same time.

 This patch has been tested on Debian jessie and unstable and requires no
 overall testing on various distros and distro versions, as we finally will
 drop all libNX_X* libraries and build against X.org's client libs.

 For now, this hack eases our development / cleanup process.

imake clean-up: Enforce build of Mesa GLX extension. Drop all other GLX build methods (built-in DRI drivers, etc.).

 The client-side library libNX_GL.{a,so} is not built when building nx-libs.

 However, nx-X11/lib/GL/** ships several imake include files
 (Imakefile.inc) that are also used in nx-X11/programs/Xserver/GL/**.
 These files have been moved from the nx-X11/lib/GL/ code subtree to the
 nx-X11/programs/Xserver/GL/.

 Furthermore, we don't provide module builds of the GL extension anymore,
 as that feature is neither used in nx-libs.

imake clean-up: Enforce build of Mesa GLX extension. Drop all other GLX build methods (built-in DRI drivers, etc.).

 The client-side library libNX_GL.{a,so} is not built when building nx-libs.

 However, nx-X11/lib/GL/** ships several imake include files
 (Imakefile.inc) that are also used in nx-X11/programs/Xserver/GL/**.
 These files have been moved from the nx-X11/lib/GL/ code subtree to the
 nx-X11/programs/Xserver/GL/.

 Furthermore, we don't provide module builds of the GL extension anymore,
 as that feature is neither used in nx-libs.