Moved more GDI definitions to gdi_private.h.
Get rid of bitmap.h and palette.h.

diff --git a/objects/metafile.c b/objects/metafile.c
index a3a9594..1c8e70c 100644
--- a/objects/metafile.c
+++ b/objects/metafile.c
@@ -50,7 +50,7 @@
 
 #include "wine/winbase16.h"
 #include "wine/wingdi16.h"
-#include "bitmap.h"
+#include "gdi.h"
 #include "wownt32.h"
 #include "winreg.h"
 #include "winternl.h"