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);
 }