DMO: blind fix for loader compilation

(cherry picked from commit 5444f9a081fa5cf74b49d4f40e13ea0675d115f5)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/codec/dmo/dmo.c

@@ -179,6 +179,10 @@ static const GUID guid_wma_enc = { 0x70f598e9, 0xf4ab, 0x495a, { 0x99, 0xe2, 0xa
 #define VLC_CODEC_MSS1      VLC_FOURCC('M','S','S','1')
 #define VLC_CODEC_MSS2      VLC_FOURCC('M','S','S','2')
 
+#ifndef BI_RGB
+# define BI_RGB 0x0
+#endif
+
 typedef struct
 {
     vlc_fourcc_t i_fourcc;