Add intra-interp experiment flag

intra-interp experiment allows intra prediction to use different
interpolation filters. It was part of the ext-intra in the nextgenv2
branch.

Change-Id: I27ab692494dc79bb92e457dbf9a72988577f1c6d
diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index 70948d0..e35bda6 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -4237,9 +4237,11 @@
 #endif  // CONFIG_EXT_PARTITION_TYPES
 #endif  // EC_ADAPT, DAALA_EC
 #if CONFIG_EXT_INTRA
+#if CONFIG_INTRA_INTERP
   for (i = 0; i < INTRA_FILTERS + 1; ++i)
     for (j = 0; j < INTRA_FILTERS - 1; ++j)
       av1_diff_update_prob(&r, &fc->intra_filter_probs[i][j], ACCT_STR);
+#endif  // CONFIG_INTRA_INTERP
 #endif  // EC_ADAPT, DAALA_EC
 
   if (frame_is_intra_only(cm)) {