fourcc: allow fallback to RGBA

XRGB was the default 32-bit RGB chroma with a mask. In some cases RGBA might be be supported, but it can't be handled locally from a XRGB source.

src/misc/fourcc.c

@@ -571,6 +571,7 @@ static const vlc_fourcc_t p_list_YUV[] = {
 static const vlc_fourcc_t p_RGB32_fallback[] = {
     VLC_CODEC_XRGB,
     VLC_CODEC_BGRX,
+    VLC_CODEC_RGBA,
     VLC_CODEC_RGB24,
     VLC_CODEC_BGR24,
     VLC_CODEC_RGB565LE,
@@ -586,6 +587,7 @@ static const vlc_fourcc_t p_RGB24_fallback[] = {
     VLC_CODEC_BGR24,
     VLC_CODEC_XRGB,
     VLC_CODEC_BGRX,
+    VLC_CODEC_RGBA,
     VLC_CODEC_RGB565LE,
     VLC_CODEC_RGB16,
     VLC_CODEC_RGB555LE,
@@ -601,6 +603,7 @@ static const vlc_fourcc_t p_RGB16_fallback[] = {
     VLC_CODEC_BGR24,
     VLC_CODEC_XRGB,
     VLC_CODEC_BGRX,
+    VLC_CODEC_RGBA,
     VLC_CODEC_RGB555LE,
     VLC_CODEC_RGB233,
     VLC_CODEC_BGR233,
@@ -615,6 +618,7 @@ static const vlc_fourcc_t p_RGB15_fallback[] = {
     VLC_CODEC_BGR24,
     VLC_CODEC_XRGB,
     VLC_CODEC_BGRX,
+    VLC_CODEC_RGBA,
     VLC_CODEC_RGB233,
     VLC_CODEC_BGR233,
     VLC_CODEC_RGB332,
@@ -631,6 +635,7 @@ static const vlc_fourcc_t p_RGB8_fallback[] = {
     VLC_CODEC_BGR24,
     VLC_CODEC_XRGB,
     VLC_CODEC_BGRX,
+    VLC_CODEC_RGBA,
     0,
 };
 static const vlc_fourcc_t *const pp_RGB_fallback[] = {