xp must be declared outside the while loop!

xp was reset in each interation despite being increased at the
iteration's end!

To protect against this happening again replace the while loop by a
for loop that references xp.

Bug introduced by d94f4727

Pixmap.c: In function ‘nxagentDisconnectAllPixmaps’:
Pixmap.c:677:19: warning: declaration of ‘r’ shadows a previous local [-Wshadow=compatible-local]
   for (int i = 0, r = 1; i < MAXCLIENTS; r = 1, i++)
                   ^
Pixmap.c:652:7: note: shadowed declaration is here
   int r = 1;
       ^
Pixmap.c: In function ‘nxagentReconnectAllPixmaps’:
Pixmap.c:840:19: warning: declaration of ‘result’ shadows a previous local [-Wshadow=compatible-local]
   for (int i = 0, result = 1; i < MAXCLIENTS; result = 1, i++)
                   ^~~~~~
Pixmap.c:807:8: note: shadowed declaration is here
   Bool result = 1;
        ^~~~~~

Display.c: In function ‘nxagentInitAndCheckVisuals’:
Display.c:2273:10: warning: declaration of ‘matched’ shadows a previous local [-Wshadow=compatible-local]
     bool matched = false;
          ^~~~~~~
Display.c:2258:8: note: shadowed declaration is here
   bool matched;
        ^~~~~~~
Display.c:2258:8: warning: unused variable ‘matched’ [-Wunused-variable]

Events.c: In function ‘nxagentDispatchEvents’:
Events.c:1241:21: warning: declaration of ‘pScreen’ shadows a previous local [-Wshadow=compatible-local]
           ScreenPtr pScreen = nxagentScreen(X.xbutton.window);
                     ^~~~~~~
Events.c:827:13: note: shadowed declaration is here
   ScreenPtr pScreen = NULL;
             ^~~~~~~
Events.c:1383:19: warning: declaration of ‘pScreen’ shadows a previous local [-Wshadow=compatible-local]
         ScreenPtr pScreen = nxagentScreen(X.xmotion.window);
                   ^~~~~~~
Events.c:827:13: note: shadowed declaration is here
   ScreenPtr pScreen = NULL;
             ^~~~~~~

Events.c: In function ‘nxagentDispatchEvents’:
Events.c:1383:19: warning: declaration of ‘pScreen’ shadows a previous local [-Wshadow=compatible-local]
         ScreenPtr pScreen = nxagentScreen(X.xmotion.window);
                   ^~~~~~~
Events.c:827:13: note: shadowed declaration is here
   ScreenPtr pScreen = NULL;
             ^~~~~~~

this was harmless but not nice nevertheless.

Clipboard.c: In function ‘nxagentConvertSelection’:
Clipboard.c:1850:9: warning: declaration of ‘i’ shadows a previous local [-Wshadow=compatible-local]
     int i = nxagentFindCurrentSelectionIndex(selection);
         ^
Clipboard.c:1736:7: note: shadowed declaration is here
   int i = nxagentFindCurrentSelectionIndex(selection);
       ^

Revert a wrong change that misteriously slipped in via the comment
reformatting commit 0133d461.

Fixes ArcticaProject/nx-libs#893

Using XlibAtom here is wrong. On a 64bit system the size of this type
is 8 bytes (64bit). At this stage we do not read Xlib datatypes but
wire datatypes. Over the wire an Atom is always 32bit, so we need to
use CARD32 here.

Fixes ArcticaProject/nx-libs#894

 Regression fix for 427b7b97. As suggested
 by Ulrich Sibiller.

 Fixes ArcticaProject/nx-libs#891.

Attributes GH PR #880: https://github.com/ArcticaProject/nx-libs/pull/880

nxagentBitmapBitOrder never existed and should really be
BitmapBitOrder. It was accidently replaced in
523009b9

used the wrong macro for length determination

nxagentPrintError is derived from XlibInt.c:_XprintDefaultError. Let's
add missing code and mark NX changes.

Backport of this xorg-xserver commit:

  commit a82e6efb7b9b2ab9a1597b002f375c5ee105e7f5
  Author: Adam Jackson <ajax@redhat.com>
  Date:   Wed Jul 16 14:19:04 2008 -0400

    Remove the numVideoScreens xprintism.

    This was to account for cases where you had video and print screens in
    the same server.  Lunacy.  Leave the slot in ScreenInfo, but rename it,
    and stop looking at it.

reqeuestingClient was dropped with the XPRINT drop. Unfortunetely we
are usign it in Image.c. So let's introduce nxagentRequestingClient as
replacement for now.

Backport from xorg-xserver:

  commit 641ce9c706ce3cbf726fb3fc9623161bb96ba127
  Author: George Sapountzis <gsap7@yahoo.gr>
  Date:   Thu Jan 3 17:28:04 2008 +0200

    drop xprint remnants: xpstubs

Needs to be an XlibAtom!

Fixes ArcticaProject/nx-libs#165

  commit dfd682b582636a36345144bcf835e3ee46718d90
  Author: Alan Coopersmith <alan.coopersmith@sun.com>
  Date:   Wed Jan 2 19:27:22 2008 -0800

    X.Org bug 4947/Sun bug 6646626: Xv extension not byte-swapping properly

    X.Org Bugzilla #4947 <https://bugs.freedesktop.org/show_bug.cgi?id=4947>
    Sun bug 6646626 <http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6646626>

    Don't use swapped data after swapping it.   When done swapping data,
    send the swapped data, not the address of the pointer to it, to the client.