BMessage: Eliminate UsePrivateHeaders kernel.

src/kits/app/Jamfile

@@ -18,7 +18,7 @@ if $(RUN_WITHOUT_APP_SERVER) != 0 {
 }
 
 UseLibraryHeaders icon ;
-UsePrivateHeaders shared app interface kernel libroot locale notification ;
+UsePrivateHeaders shared app interface libroot locale notification ;
 
 SetSubDirSupportedPlatforms haiku libbe_test ;
 

src/kits/app/Message.cpp

@@ -15,7 +15,7 @@
 #include <DirectMessageTarget.h>
 #include <MessengerPrivate.h>
 #include <TokenSpace.h>
-#include <util/KMessage.h>
+#include <kernel/util/KMessage.h>
 
 #include <Alignment.h>
 #include <Application.h>