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/common/filter.c b/av1/common/filter.c
index 3f1cdbb..0d6bc3b 100644
--- a/av1/common/filter.c
+++ b/av1/common/filter.c
@@ -194,12 +194,14 @@
 #endif  // CONFIG_EXT_INTERP
 
 #if CONFIG_EXT_INTRA
+#if CONFIG_INTRA_INTERP
 const InterpKernel *av1_intra_filter_kernels[INTRA_FILTERS] = {
   bilinear_filters,         // INTRA_FILTER_LINEAR
   sub_pel_filters_8,        // INTRA_FILTER_8TAP
   sub_pel_filters_8sharp,   // INTRA_FILTER_8TAP_SHARP
   sub_pel_filters_8smooth,  // INTRA_FILTER_8TAP_SMOOTH
 };
+#endif  // CONFIG_INTRA_INTERP
 #endif  // CONFIG_EXT_INTRA
 
 #if CONFIG_EXT_INTERP