Add a few missing #includes.
diff --git a/dlls/mapi32/imalloc.c b/dlls/mapi32/imalloc.c
index ffe20ed..1ea9442 100644
--- a/dlls/mapi32/imalloc.c
+++ b/dlls/mapi32/imalloc.c
@@ -31,6 +31,7 @@
 #include "winternl.h"
 #include "objbase.h"
 #include "shlwapi.h"
+#include "mapiutil.h"
 #include "wine/debug.h"
 
 WINE_DEFAULT_DEBUG_CHANNEL(mapi);