Got dropped by accident in 9bc6ff26

Fixes ArcticaProject/nx-libs#589

 Fixes ArcticaProject/nx-libs#546.

nx-X11/{config/cf/{{Imake,X11}.tmpl,linux.cf},programs/Xserver/{include/os.h,os/{Imakefile,reallocarray.c}}: backport reallocarray() implementation.

nx-X11/config/cf/X11.tmpl: Set a more appropriate font directory (recommended: /usr/{,local/}share/nx/fonts).

 Note for distribution maintainers: your normally want to
 symlink /usr/share/nx/fonts to /usr/share/fonts/X11 in
 your packaging.

Xserver/os/oscolor.c: Follow X.org in dropping the rgb.txt file entirely. Content of that file is now hard-coded.

 Adopting an exact copy of os/oscolor.c from X.org leads to this compiler warning:

 ```
 oscolor.c:844:1: warning: string length ‘7614’ is greater than the length ‘4095’ ISO C99 compilers are required to support [-Woverlength-strings]
 };
 ^
 ```

 This will be address later in coordination with X.org.

 Note: there is a tiny change in oscolor.c as we ship it. The original X.org file includes <X11/keysym.h> which seems
 unneeded. We drop that one line from oscolor.c.

 Fixes ArcticaProject/nx-libs#259.

nx-X11/config/cf/X11.tmpl: Set a more appropriate font directory (recommended: /usr/{,local/}share/nx/fonts).

 Note for distribution maintainers: your normally want to
 symlink /usr/share/nx/fonts to /usr/share/fonts/X11 in
 your packaging.

Xserver/os/oscolor.c: Follow X.org in dropping the rgb.txt file entirely. Content of that file is now hard-coded.

 Adopting an exact copy of os/oscolor.c from X.org leads to this compiler warning:

 ```
 oscolor.c:844:1: warning: string length ‘7614’ is greater than the length ‘4095’ ISO C99 compilers are required to support [-Woverlength-strings]
 };
 ^
 ```

 This will be address later in coordination with X.org.

 Note: there is a tiny change in oscolor.c as we ship it. The original X.org file includes <X11/keysym.h> which seems
 unneeded. We drop that one line from oscolor.c.

 Fixes ArcticaProject/nx-libs#259.

just as Xorg upstream did

 Fixes ArcticaProject/nx-libs#250.

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

  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.