Add AVX2 variant for av1_ext_warp_affine

Added AVX2 variant for av1_ext_warp_affine
function and unit test (AV1ExtWarpFilterTest).

Module gains improved by factor of ~5.79x w.r.t. C module.

Change-Id: Ie6d0932b4f45500904f6eddf7f453a8bd1aa98f0
diff --git a/av1/common/warped_motion.h b/av1/common/warped_motion.h
index 3b9c4a6..1fd25d0 100644
--- a/av1/common/warped_motion.h
+++ b/av1/common/warped_motion.h
@@ -39,6 +39,13 @@
 DECLARE_ALIGNED(8, extern const int8_t,
                 av1_filter_8bit[WARPEDPIXEL_PREC_SHIFTS * 3 + 1][8]);
 
+#if CONFIG_EXT_WARP
+extern const int16_t av1_ext_warped_filter[WARPEDPIXEL_PREC_SHIFTS + 1][8];
+
+DECLARE_ALIGNED(16, extern const int16_t,
+                av1_ext_filter_16bit[WARPEDPIXEL_PREC_SHIFTS + 1][8]);
+#endif  // CONFIG_EXT_WARP
+
 /* clang-format off */
 static const int error_measure_lut[512] = {
     // pow 0.7