Backported-to-nx-by: Ulrich Sibiller <uli42@gmx.de>

    commit 8a34d7a8532c7ca013e67307f3baf200167abb92
    Author: Ander Conselvan de Oliveira <ander.conselvan-de-oliveira@nokia.com>
    Date:   Tue Feb 8 11:10:11 2011 +0200

      XkbSendNames: fix use of uninitialised bytes valgrind error.

      ==537== Syscall param writev(vector[...]) points to uninitialised byte(s)
      ==537==    at 0x4AB7154: writev (writev.c:51)
      ==537==    by 0x8935B: _XSERVTransWritev (Xtrans.c:912)
      ==537==    by 0x6C55F: FlushClient (io.c:924)
      ==537==    by 0x6CCF3: WriteToClient (io.c:846)
      ==537==    by 0xD51D3: XkbSendNames (xkb.c:3765)
      ==537==    by 0xD8183: ProcXkbGetKbdByName (xkb.c:5825)
      ==537==    by 0x27B7B: Dispatch (dispatch.c:432)
      ==537==    by 0x205B7: main (main.c:291)
      ==537==  Address 0x55899f2 is 154 bytes inside a block of size 1,896 alloc'd
      ==537==    at 0x4834C48: malloc (vg_replace_malloc.c:236)
      ==537==    by 0xD47AF: XkbSendNames (xkb.c:3642)
      ==537==    by 0xD8183: ProcXkbGetKbdByName (xkb.c:5825)
      ==537==    by 0x27B7B: Dispatch (dispatch.c:432)
      ==537==    by 0x205B7: main (main.c:291)
      ==537==  Uninitialised value was created by a heap allocation
      ==537==    at 0x4834C48: malloc (vg_replace_malloc.c:236)
      ==537==    by 0xD47AF: XkbSendNames (xkb.c:3642)
      ==537==    by 0xD8183: ProcXkbGetKbdByName (xkb.c:5825)
      ==537==    by 0x27B7B: Dispatch (dispatch.c:432)
      ==537==    by 0x205B7: main (main.c:291)
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Oliver McFadden <oliver.mcfadden@nokia.com>
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan-de-oliveira@nokia.com>

an empty nxagentKeyboard variable is no reason to fall back to no-XKB mode

most of the code was existing twice

manpage does not tell us if NULL is valid

use the ones from xkb

Just use the existing xkb code

Defines regarding XKB-BASE_DIRECTORY are used only xkb.

Attributes GH PR #734: https://github.com/ArcticaProject/nx-libs/pull/734

Attributes GH PR #732: https://github.com/ArcticaProject/nx-libs/pull/732

Attributes GH PR #731: https://github.com/ArcticaProject/nx-libs/pull/731