free() can handle NULL itself

Fixes ArcticaProject/nx-libs#569

Attributes GH PR #582: https://github.com/ArcticaProject/nx-libs/pull/582

nxagent will abort if it encounters an unknown command line option. As
we want 3.6 to be a drop-in replacement for 3.5 we cannot simply drop old
options but must accept them as no-op.

Attributes GH PR #588: https://github.com/ArcticaProject/nx-libs/pull/588

Fixes: ArcticaProject/nx-libs#585

It is called only if DEBUG_TREE is defined.

Fixes ArcticaProject/nx-libs#585

Attributes GH PR #581: https://github.com/ArcticaProject/nx-libs/pull/581

Fixes: ArcticaProject/nx-libs#558
Fixes: ArcticaProject/nx-libs#541
Fixes: ArcticaProject/nx-libs#542

Backported from X.org:

   commit 512bac25ec0e980968b93a2ebe88bd89bf99b697
   Author: Daniel Stone <daniel@fooishbar.org>
   Date:   Tue Nov 6 14:52:03 2007 +0000

    DIX: XKB: Set xkbInfo to NULL as well as freeing it (bug # 10639)

    XkbRemoveResourceClient wants to access xkbInfo if it exists, so make
    sure we NULL it after freeing it.  It doesn't make much sense to move
    the RemoveResourceClient call first, as there's not much point in
    notifying clients while we're shutting the server down anyway.
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>

Backported from X.Org:

   commit 1cfa9f647e0241f4b9e56556b128d7bfd987eaca
   Author: Daniel Stone <daniel@fooishbar.org>
   Date:   Tue Feb 28 16:55:26 2006 +0000

   Bug # 5216: Allow options to appear with other components.
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>

Backported from X.Org:

    commit 0693083335185ce05ee64546151f3fc43ce98575
    Author: Lars Knoll <lars@trolltech.com>
    Date:   Mon Mar 6 21:00:09 2006 +0000

    render/picture.c Correctly initialize devPrivates variable in source only
        pictures to 0
    miext/cw/cw.h Don't try to access devPrivates of source only pictures
Backported-from-NX-by: Ulrich Sibiller <uli42@gmx.de>

Backported from X.org:

   Commit 6bb2dc02a7cffd6ed7dd28e88d584920a4150749
   Author: Adam Jackson <ajax@nwnk.net>
   Date:   Wed Mar 15 16:01:47 2006 +0000

   Coverity # 337: Remove useless NULL check.
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>

Backported from X.org:

   commit 72cc6307257fcbb800267464487bf918ee674328
   Author: Adam Jackson <ajax@nwnk.net>
   Date:   Wed Mar 15 16:32:05 2006 +0000

   Coverity # 491: Check version number correctly.
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>

Backported from X.org:

   commit 152090ce442e94de1ae920208a92931af6493c8c
   Author: Adam Jackson <ajax@nwnk.net>
   Date:   Wed Mar 15 16:33:12 2006 +0000

   Coverity # 487: Check version number correctly.
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>

Fixes ArcticaProject/nx-libs#542

Backported from X.org:

   commit 5e106a71b9f8077216d41619402952b0005dd8a4
   Author: Adam Jackson <ajax@nwnk.net>
   Date:   Wed Mar 15 16:49:04 2006 +0000

   Coverity # 807: Fix a memory leak in XFixesExpandRegion.
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>

Fixes ArcticaProject/nx-libs#541

Backported from X.org:

   commit fc7fb5bbe1c8f787e53500b9a2ca4af815f310d1
   Author: Giuseppe Bilotta giuseppe.bilotta@gmail.com
   Date: Thu Nov 9 10:21:21 2017 +0100

   randr: free crtc->outputs on destroy
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>

Fixes ArcticaProject/nx-libs#558

Backported from X.org:

   commit 16381d186e7c791031392ed8afcfd33009854e9e
   Author: Giuseppe Bilotta giuseppe.bilotta@gmail.com
   Date: Thu Nov 9 10:21:20 2017 +0100

   randr: always realloc crtcs and outputs

   When the last crtc (resp. output) is destroyed, the rrScrPriv crtcs
   (resp. outputs) fields do not get cleared, which can lead to a situation
   where the private's numCrtcs (resp. numOutputs) field is zero, but the
   associated memory is still allocated. Just checking if numCrtcs (resp.
   numOutputs) is zero is thus not a good criteria to determine whetehr to
   use a realloc or a malloc.

   Since crtcs (resp. outputs) are NULL-initialized anyway, relying on
   numCrtcs (resp. numOutputs) is actually unnecessary, because
   reallocation of a NULL ptr is equivalent to a malloc anyway.

   Therefore, just use realloc() unconditionally, and ensure that the
   fields are properly initialized.
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>

Fixes ArcticaProject/nx-libs#558

Attributes GH PR #578: https://github.com/ArcticaProject/nx-libs/pull/578

Attributes GH PR #562: https://github.com/ArcticaProject/nx-libs/pull/562

Fixes: ArcticaProject/nx-libs#546
Fixes: ArcticaProject/nx-libs#547

 Fixes ArcticaProject/nx-libs#547.

 Fixes ArcticaProject/nx-libs#546.

Attributes GH PR #579: https://github.com/ArcticaProject/nx-libs/pull/579

Some functions' return values are never used anywhere, so drop them.

This corrects a flaw that stayed undetected for 2.5 years, introduced via
c5a2cf82

Fixes ArcticaProject/nx-libs#573

Attributes GH PR #556: https://github.com/ArcticaProject/nx-libs/pull/556

Adds a new option called "keyconv" to control keycode conversion.

Before commit 2f2ade61 keycode
conversion was activated if the client was Linux and client side rules
and/or model was "evdev". The only (and undocumented) way to disable
that was providing a value different from "linux" for the "client"
option (which had no other effect). The mentioned commit removed the
dependency on Linux and so there was no way anymore to disable keycode
conversion.

Attributes GH PR #563: https://github.com/ArcticaProject/nx-libs/pull/563