avcodec/utvideodec: decode to GBR(A)P

This is actually internal utvideo format.
Allows to make use of SIMD for median prediction for rgb(a) formats,
thus speeding up decoding.
Simplifies code, eases further developement and maintenance.

Update FATE because of pixel format switch.
Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/utvideo.h

@@ -63,9 +63,6 @@ enum {
 /* Mapping of libavcodec prediction modes to Ut Video's */
 extern const int ff_ut_pred_order[5];
 
-/* Order of RGB(A) planes in Ut Video */
-extern const int ff_ut_rgb_order[4];
-
 typedef struct UtvideoContext {
     const AVClass *class;
     AVCodecContext *avctx;

tests/ref/fate/utvideo_rgb_left

@@ -3,7 +3,7 @@
 #codec_id 0: rawvideo
 #dimensions 0: 640x480
 #sar 0: 0/1
-0,          0,          0,        1,   921600, 0x27e6001e
-0,          1,          1,        1,   921600, 0x7c0a92bc
-0,          2,          2,        1,   921600, 0x4d2be42c
-0,          3,          3,        1,   921600, 0x58ddd0be
+0,          0,          0,        1,   921600, 0xb457001e
+0,          1,          1,        1,   921600, 0xceff92bc
+0,          2,          2,        1,   921600, 0x762de42c
+0,          3,          3,        1,   921600, 0xef14d0be

tests/ref/fate/utvideo_rgb_median

@@ -3,8 +3,8 @@
 #codec_id 0: rawvideo
 #dimensions 0: 640x480
 #sar 0: 0/1
-0,          0,          0,        1,   921600, 0x9776611f
-0,          1,          1,        1,   921600, 0xdbfa64f4
-0,          2,          2,        1,   921600, 0xed2a0580
-0,          3,          3,        1,   921600, 0x6ecc80bc
-0,          4,          4,        1,   921600, 0x58ddd0be
+0,          0,          0,        1,   921600, 0x85af611f
+0,          1,          1,        1,   921600, 0xc97a64f4
+0,          2,          2,        1,   921600, 0xb1db0580
+0,          3,          3,        1,   921600, 0xa18d80bc
+0,          4,          4,        1,   921600, 0xef14d0be

tests/ref/fate/utvideo_rgba_left

@@ -3,8 +3,8 @@
 #codec_id 0: rawvideo
 #dimensions 0: 640x480
 #sar 0: 0/1
-0,          0,          0,        1,  1228800, 0xf1bc9432
-0,          1,          1,        1,  1228800, 0x8480d1e5
-0,          2,          2,        1,  1228800, 0xb01d5fb2
-0,          3,          3,        1,  1228800, 0x53cb42c4
-0,          4,          4,        1,  1228800, 0x2b2ea176
+0,          0,          0,        1,  1228800, 0xf9f49432
+0,          1,          1,        1,  1228800, 0xf089d1e5
+0,          2,          2,        1,  1228800, 0xbd025fb2
+0,          3,          3,        1,  1228800, 0x17bf42c4
+0,          4,          4,        1,  1228800, 0xe31ea176

tests/ref/fate/utvideo_rgba_median

@@ -3,8 +3,8 @@
 #codec_id 0: rawvideo
 #dimensions 0: 640x480
 #sar 0: 0/1
-0,          0,          0,        1,  1228800, 0xf1bc9432
-0,          1,          1,        1,  1228800, 0x8480d1e5
-0,          2,          2,        1,  1228800, 0xb01d5fb2
-0,          3,          3,        1,  1228800, 0x53cb42c4
-0,          4,          4,        1,  1228800, 0x2b2ea176
+0,          0,          0,        1,  1228800, 0xf9f49432
+0,          1,          1,        1,  1228800, 0xf089d1e5
+0,          2,          2,        1,  1228800, 0xbd025fb2
+0,          3,          3,        1,  1228800, 0x17bf42c4
+0,          4,          4,        1,  1228800, 0xe31ea176

tests/ref/fate/utvideo_rgba_single_symbol

@@ -3,4 +3,4 @@
 #codec_id 0: rawvideo
 #dimensions 0: 1024x768
 #sar 0: 0/1
-0,          0,          0,        1,  3145728, 0xac95c593
+0,          0,          0,        1,  3145728, 0xa07dc593