vp9: add fate test for intraonly frames.

Sample available at:
http://downloads.webmproject.org/test_data/libvpx/vp90-2-16-intra-only.webm

tests/fate/vpx.mak

@@ -104,6 +104,7 @@ $(eval $(call FATE_VP9_SUITE,09-lf_deltas,$(1),$(2)))
 $(eval $(call FATE_VP9_SUITE,10-show-existing-frame,$(1),$(2)))
 $(eval $(call FATE_VP9_SUITE,10-show-existing-frame2,$(1),$(2)))
 $(eval $(call FATE_VP9_SUITE,15-segkey_adpq,$(1),$(2)))
+$(eval $(call FATE_VP9_SUITE,16-intra-only,$(1),$(2)))
 $(eval $(call FATE_VP9_SUITE,2pass-akiyo,$(1),$(2)))
 $(eval $(call FATE_VP9_SUITE,parallelmode-akiyo,$(1),$(2)))
 $(eval $(call FATE_VP9_SUITE,segmentation-aq-akiyo,$(1),$(2)))

tests/ref/fate/vp9-16-intra-only

+#format: frame checksums
+#version: 1
+#hash: MD5
+#tb 0: 12/359
+#stream#, dts,        pts, duration,     size, hash
+0,          0,          0,        1,   152064, d57529601178948afa4818c3c8938884
+0,          1,          1,        1,   152064, d47e00250c45733d64af067a417bcd06
+0,          2,          2,        1,   152064, 984e41cd8350808ac6129746b2377818
+0,          4,          4,        1,   152064, 76ba63001170b8992fc72be5c4ace731
+0,          5,          5,        1,   152064, c4e7f96a8fd58d901b1d881926ddae09