fate: force the simple idct for xvid custom matrix test

The original test without a forced idct is still useful since it tests
the switching of the idct algorithm/permutation on x86 with MMX. MMXext
or SSE2. Make sure the test runs only if MMX inline asm is available and
force -cpuflags to all.
Add the required bitexact flag for both tests.

tests/fate/xvid.mak

-fate-xvid-custom-matrix: CMD = framemd5 -i $(TARGET_SAMPLES)/mpeg4/xvid_vlc_trac7411.h263
+fate-xvid-custom-matrix: CMD = framemd5 -flags +bitexact -idct simple  -i $(TARGET_SAMPLES)/mpeg4/xvid_vlc_trac7411.h263
+fate-xvid-idctmmx:       CMD = framemd5 -flags +bitexact -cpuflags all -i $(TARGET_SAMPLES)/mpeg4/xvid_vlc_trac7411.h263
 
 FATE_XVID-$(call DEMDEC, M4V, MPEG4) += fate-xvid-custom-matrix
+FATE_XVID-$(filter $(HAVE_MMX_INLINE), $(call DEMDEC, M4V, MPEG4)) += fate-xvid-idctmmx
+
 FATE_SAMPLES_AVCONV += $(FATE_XVID-yes)
 
 fate-xvid: $(FATE_XVID-yes)

tests/ref/fate/xvid-custom-matrix

 #tb 0: 1/25
-0,          1,          1,        1,   622080, fec19d49e4433046ac5f7a9f3dff2078
-0,          2,          2,        1,   622080, 77aa1a369ce3e180648eaccce95cb618
-0,          3,          3,        1,   622080, d3ff08bc77e247a4b033d37ff780c2a2
-0,          4,          4,        1,   622080, 362c6b7411f23134880b4ceeaf09aafb
-0,          5,          5,        1,   622080, 52ba7f7611160ed9516a3b94dd889254
-0,          6,          6,        1,   622080, e11bf4956dfa43a760cdb8a6c46201eb
-0,          7,          7,        1,   622080, 5305b5775b9481b136e84c0f1c2c52c7
-0,          8,          8,        1,   622080, 65510ff0135a41e5acc99071893c99b2
-0,          9,          9,        1,   622080, cab3a8991f0d404bb42386efb430abc7
-0,         10,         10,        1,   622080, b7a8305768527a9b54248e620a5e7117
-0,         11,         11,        1,   622080, 67adbfe7c321a2a74244d2a268de598a
-0,         12,         12,        1,   622080, 9bcaed10aa15b8a5278c5c4840cfb9c8
-0,         13,         13,        1,   622080, 0e3065f441313496cb390ba1a6c92b11
-0,         14,         14,        1,   622080, f741816f762c000fc6fa77d9d1d96cdc
-0,         15,         15,        1,   622080, 259686747b597c168440d5cfe75cdfbf
-0,         16,         16,        1,   622080, d37341f0bea41b6d0421e984cd079673
-0,         17,         17,        1,   622080, 97428665f84e4364bdba768ad604bcdc
-0,         18,         18,        1,   622080, 8c32ce967ee34df1ccbdf4e8b6aa8c8d
-0,         19,         19,        1,   622080, 7fee903f21d29d6d8215fc04c8b3af34
-0,         20,         20,        1,   622080, 3d67c55cc62f0308cd4549c7ac46081a
+0,          1,          1,        1,   622080, 870e846b6b001d3e34fa87df96297e28
+0,          2,          2,        1,   622080, de1a3dd9fcc32086ecdffd4591a8defa
+0,          3,          3,        1,   622080, 59f5f16d4224e98e09f22818cc9227e0
+0,          4,          4,        1,   622080, 9744609bcf95107bdbe6a9e21dc22b9d
+0,          5,          5,        1,   622080, 6dc50ad4b5821cc20f418f2eb273a45c
+0,          6,          6,        1,   622080, 57012fc77d853c17591319cc528ebd93
+0,          7,          7,        1,   622080, fd0068955ce1583f21bb888ad3b6952a
+0,          8,          8,        1,   622080, 58b7bcb056fac5d34ec4197fe10723a7
+0,          9,          9,        1,   622080, 064311346d0ea2753f01f18f13188c27
+0,         10,         10,        1,   622080, 21995e49367aee152a11992f48317bbe
+0,         11,         11,        1,   622080, 288c2cd0ac0a3b74d23da6ba30111d55
+0,         12,         12,        1,   622080, 88db7bf240fd6ee5ef89c34522de76e8
+0,         13,         13,        1,   622080, 8e2d38686bbf768e812005decc37cb90
+0,         14,         14,        1,   622080, 3a7d3c036ecaa669d26660937a8b723e
+0,         15,         15,        1,   622080, 6c8b8e847c544125213c9f49d9607d98
+0,         16,         16,        1,   622080, 16b56117f1b327862f78421116dfe52e
+0,         17,         17,        1,   622080, a7ce423456a59bdb4d5921aff1a27691
+0,         18,         18,        1,   622080, 881c9561c9ab66a7659145173f8e8cda
+0,         19,         19,        1,   622080, 7413961f9accd1d32e116592a6448e9b
+0,         20,         20,        1,   622080, c66409494fd1714e6236596f476cece6

tests/ref/fate/xvid-idctmmx

+#tb 0: 1/25
+0,          1,          1,        1,   622080, 8fe318df973b5d7669e6d28ebf03b229
+0,          2,          2,        1,   622080, 3568d92074e0298a2027f990004fe1a6
+0,          3,          3,        1,   622080, 4781afb6ba38318738e26a98ace4061b
+0,          4,          4,        1,   622080, bd29a005b8392005ef30211f185ca049
+0,          5,          5,        1,   622080, fc50b441ee9256883edba5a584000d66
+0,          6,          6,        1,   622080, 5fce9fb7e66c9d0773ff9c7482cb8307
+0,          7,          7,        1,   622080, 2e0ad7b1ba39e60cdd7a65ed1ed57c30
+0,          8,          8,        1,   622080, b91cfdb91751dabd6691d3c34221b636
+0,          9,          9,        1,   622080, f65507bc00043e8fe345c542f0861a64
+0,         10,         10,        1,   622080, 2e4ee4ea4ec761c2298acced17f63f35
+0,         11,         11,        1,   622080, e7945bd07296205d1549c8edf843af48
+0,         12,         12,        1,   622080, 52fed0ec02c57a138de7dc0e0c804de8
+0,         13,         13,        1,   622080, 3ee2848d0d70795e14765127111a677c
+0,         14,         14,        1,   622080, 42cb0929406b10b95817ffaa2da47335
+0,         15,         15,        1,   622080, 523986866b6cf729e130ea43feacb0a2
+0,         16,         16,        1,   622080, 5d1e4becddf728e93bbcb428de1f02ae
+0,         17,         17,        1,   622080, 0a1453df21e4547447ec8f27a0d4d5ec
+0,         18,         18,        1,   622080, d3495686e769df299b1732326fa3f17e
+0,         19,         19,        1,   622080, 602e9020397b1e82b58b1ff6b9733d21
+0,         20,         20,        1,   622080, 759bd3f739a3b99309efa5c1a697e34d