include: move private definitions out of extinit.h

Public server module API shouldn't be clobbered with private definitions,
thus move them out to extinit_priv.h.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1289>

Xext/shm.c

@@ -41,7 +41,10 @@ in this Software without prior written authorization from The Open Group.
 #include <fcntl.h>
 #include <X11/X.h>
 #include <X11/Xproto.h>
+#include <X11/extensions/shmproto.h>
+#include <X11/Xfuncproto.h>
 
+#include "dix/dix_priv.h"
 #include "os/auth.h"
 #include "os/busfault.h"
 #include "os/osdep.h"
@@ -58,9 +61,7 @@ in this Software without prior written authorization from The Open Group.
 #include "servermd.h"
 #include "shmint.h"
 #include "xace.h"
-#include <X11/extensions/shmproto.h>
-#include <X11/Xfuncproto.h>
-#include <sys/mman.h>
+#include "extinit_priv.h"
 #include "protocol-versions.h"
 
 /* Needed for Solaris cross-zone shared memory extension */
@@ -95,10 +96,6 @@ in this Software without prior written authorization from The Open Group.
 #include "panoramiXsrv.h"
 #endif
 
-#include "dix/dix_priv.h"
-
-#include "extinit.h"
-
 typedef struct _ShmScrPrivateRec {
     CloseScreenProcPtr CloseScreen;
     ShmFuncsPtr shmFuncs;