no function change

Attributes GH PR #864: https://github.com/ArcticaProject/nx-libs/pull/864

NXxvdisp.c only exists to set/unset nxagentXvTrap before/after
dispatch. There's no need to duplicate the original code. We now
rename the original dispatch functions and call them in our dispatch
code.

Also drop check for sun and cygwin, as they never appeared in xorg
upstream code.

Attributes GH PR #863: https://github.com/ArcticaProject/nx-libs/pull/863

by calling the upstream function from dix/dispatch.c

remove ~80 duplicate lines

by calling upstream version from dispatch.c

Attributes GH PR #861: https://github.com/ArcticaProject/nx-libs/pull/861

instead of including it and creating NXextension.o we can simply use
the dix version. There are no NX specials anymore.

Attributes GH PR #859: https://github.com/ArcticaProject/nx-libs/pull/859

instead of having an identical copy in nxagent_miShmPutImage

instead of having an own (identical) copy

Attributes GH PR #856: https://github.com/ArcticaProject/nx-libs/pull/856

The only left code was nxagentCheckum() which was not compiling anyway.

Attributes GH PR #870: https://github.com/ArcticaProject/nx-libs/pull/870

With the previous commits this file finally becomes obsolete.

This backport of a 2013 Xorg fix changes miext/damage.c so that the
text functions (damageText, damage{Poly,Image}Text{8,16}) finally are
very similar to the changes that NX introduced in 2007 with
nxagent-3.0.0-28.

Fun fact: the original freedesktop bug mentioned below is from 2005
and the fix came in 2013...

Next commit will be the complete drop of NXdamage.c.

  commit 0f3f8e4295d4c05f33b93e0ffd2f6f8cd5759bf7
  Author: Adam Jackson <ajax@redhat.com>
  Date:   Wed Aug 21 11:13:11 2013 -0400

    damage: Don't rewrite Text ops to GlyphBlt ops

    There's no particularly good reason to, and it breaks Xnest.

    Bugzilla: http://bugs.freedesktop.org/2454Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Adam Jackson <ajax@redhat.com>

f0ba303d errornously added the "else"
which had been explicitly removed in NX 3.0.0-28 with this comment:

- Changed damage's GCOps functions drawing text. This was needed be-
  cause the original functions didn't call agent GCOps if the drawable
  was registered for damage events.

Attributes GH PR #858: https://github.com/ArcticaProject/nx-libs/pull/858

add a callback to determine the starting window.

Our version only adds some commented code, so it is not really
necessary. But it is cleaner to handle it that way.

Attributes GH PR #851: https://github.com/ArcticaProject/nx-libs/pull/851

Backport of this commit:

  commit 7ba7085b4f01f3cd72008712a5333ea3f0edfd88
  Author: walter harms <wharms@bfs.de>
  Date:   Sat Oct 28 19:14:22 2017 +0200

    AuRead.c: remove redundant null check on calling free()

    this removes simply unneeded code from XauReadAuth
Signed-off-by: Walter Harms <wharms@bfs.de>
Reviewed-by: Daniel Martin <consume.noise@gmail.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

libXau is integrated into libNX_X11, but the differences to libXau
original code where not explicitly marked. This path adds some ifdefs
and also restores the original code.

Attributes to ArcticaProject/nx-libs#850

Attributes GH PR #845: https://github.com/ArcticaProject/nx-libs/pull/845

nxagent links system libraries that link against libX11. Unfortunately,
nxagent (and libXcompshad) require a modified libX11 version,
nicknamed libNX_X11, for proper functioning. Fortunately, this one can
act as a drop-in replacement for the system libX11. So we’ll hack our
way out: add a DT_NEEDED entry for libX11 by linking against the
system library when building nxagent and link the other system
libraries later and set DT_RUNPATH to a special directory containing
symlinks from libNX_X11 to libX11.

This tricks the loader into pulling in the "fake" libX11 version
without checking its SONAME and thus satisfying the DT_NEEDED entry
early on - specifically also for the system libraries.

Ex.:
readelf -a /usr/bin/nxagent | grep NEEDED
 0x0000000000000001 (NEEDED)             Shared library: [libX11.so.6]
...
 0x0000000000000001 (NEEDED)             Shared library: [libNX_X11.so.6]
...

If, however, you run the build a second time, it will find the newly
created libX11 links in ../../exports/lib (used as an additional
library search path) instead of the system libX11. The results in a
binary looking like this:

 0x0000000000000001 (NEEDED)             Shared library: [libNX_X11.so.6]
...

With such a setup, the whole magic falls apart and system libraries
will suddenly pull in the actual system libX11 file.

We initially believed a compiler call such as:

${CC} [--unrelated-options ...] [-Lunrelated_library_path ...] -lX11 [more
       options like -l and -L] -L../../exports/lib -lother_libraries

to do "the right thing" and link against the system libX11 (or, at
worst, a libX11 found in the library directory search list preceding the
link call) and use ../../exports/lib only for later linking operations,
since the order of options matters.

However, this turned out to be blatantly wrong: while the order of -L
arguments does matter for building the search path, the whole search
path including elements from *ALL* -L arguments (and the system paths)
will always be used when linking libraries.

Hence, (counter-intuitively to us) both these calls will be equivalent:

${CC} [--unrelated-options ...] -la -Loverride_liba -lb
      [-Lunrelated_library_path ...] -lc

${CC} [--unrelated-options ...] -Loverride_liba [-Lunrelated_library_path
       ...] -la -lb -lc

By removing LDPRELIBS from NXAGENTSYSLIBS, ../../exports/lib is no
longer used during building/linking and the binaries are built
reproducibly. We never intended to use this directory at link time
anyway.

Attributes GH PR #849: https://github.com/ArcticaProject/nx-libs/pull/849