Moved FatalAppExit functions to win32/except.c.
Added a few uses of Callout instead of referencing USER functions
directly.

diff --git a/misc/comm.c b/misc/comm.c
index 0f9bf1e..6d49786 100644
--- a/misc/comm.c
+++ b/misc/comm.c
@@ -68,6 +68,7 @@
 #include "process.h"
 #include "winerror.h"
 #include "services.h"
+#include "callback.h"
 #include "file.h"
 
 #include "debugtools.h"
@@ -298,7 +299,7 @@
   /* send notifications, if any */
   if (ptr->wnd && mask) {
     TRACE("notifying %04x: cid=%d, mask=%02x\n", ptr->wnd, cid, mask);
-    PostMessage16(ptr->wnd, WM_COMMNOTIFY, cid, mask);
+    Callout.PostMessage16(ptr->wnd, WM_COMMNOTIFY, cid, mask);
   }
 }
 
diff --git a/misc/printdrv.c b/misc/printdrv.c
index 8b19090..ae6b39d 100644
--- a/misc/printdrv.c
+++ b/misc/printdrv.c
@@ -603,8 +603,7 @@
 
     TRACE("%04x %04x '%s'\n", hJob,  cchMsg, lpMsg);
 
-    nRet = MessageBox16(0, lpMsg, "Printing Error", MB_OKCANCEL);
-    return nRet;
+    return Callout.MessageBoxA(0, lpMsg, "Printing Error", MB_OKCANCEL);
 }
 
 
diff --git a/win32/except.c b/win32/except.c
index f642481..c76d438 100644
--- a/win32/except.c
+++ b/win32/except.c
@@ -31,6 +31,7 @@
 #include "ntddk.h"
 #include "wine/exception.h"
 #include "ldt.h"
+#include "callback.h"
 #include "process.h"
 #include "thread.h"
 #include "stackframe.h"
@@ -92,7 +93,7 @@
     sprintf( message, "Unhandled exception 0x%08lx at address 0x%08lx.",
              epointers->ExceptionRecord->ExceptionCode,
              (DWORD)epointers->ExceptionRecord->ExceptionAddress );
-    MessageBoxA( 0, message, "Error", MB_OK | MB_ICONHAND );
+    Callout.MessageBoxA( 0, message, "Error", MB_OK | MB_ICONHAND );
     return EXCEPTION_EXECUTE_HANDLER;
 }
 
@@ -110,6 +111,38 @@
 }
 
 
+/**************************************************************************
+ *           FatalAppExit16   (KERNEL.137)
+ */
+void WINAPI FatalAppExit16( UINT16 action, LPCSTR str )
+{
+    WARN("AppExit\n");
+    FatalAppExitA( action, str );
+}
+
+
+/**************************************************************************
+ *           FatalAppExitA   (KERNEL32.108)
+ */
+void WINAPI FatalAppExitA( UINT action, LPCSTR str )
+{
+    WARN("AppExit\n");
+    Callout.MessageBoxA( 0, str, NULL, MB_SYSTEMMODAL | MB_OK );
+    ExitProcess(0);
+}
+
+
+/**************************************************************************
+ *           FatalAppExitW   (KERNEL32.109)
+ */
+void WINAPI FatalAppExitW( UINT action, LPCWSTR str )
+{
+    WARN("AppExit\n");
+    Callout.MessageBoxW( 0, str, NULL, MB_SYSTEMMODAL | MB_OK );
+    ExitProcess(0);
+}
+
+
 /*************************************************************
  *            WINE_exception_handler
  *
diff --git a/windows/msgbox.c b/windows/msgbox.c
index 62495c2..4d6db88 100644
--- a/windows/msgbox.c
+++ b/windows/msgbox.c
@@ -399,37 +399,3 @@
 
     return MessageBoxIndirectA(&msgboxa);
 }
-
-
-/**************************************************************************
- *           FatalAppExit16   (KERNEL.137)
- */
-void WINAPI FatalAppExit16( UINT16 action, LPCSTR str )
-{
-    WARN("AppExit\n");
-    FatalAppExitA( action, str );
-}
-
-
-/**************************************************************************
- *           FatalAppExit32A   (KERNEL32.108)
- */
-void WINAPI FatalAppExitA( UINT action, LPCSTR str )
-{
-    WARN("AppExit\n");
-    MessageBoxA( 0, str, NULL, MB_SYSTEMMODAL | MB_OK );
-    ExitProcess(0);
-}
-
-
-/**************************************************************************
- *           FatalAppExit32W   (KERNEL32.109)
- */
-void WINAPI FatalAppExitW( UINT action, LPCWSTR str )
-{
-    WARN("AppExit\n");
-    MessageBoxW( 0, str, NULL, MB_SYSTEMMODAL | MB_OK );
-    ExitProcess(0);
-}
-
-