Allow specifying opt dependencies

If optimizations use more than one cpu feature, allow
specifying them so that '--disable-X' still works

https://code.google.com/p/webm/issues/detail?id=854

Change-Id: I3108ea37b397371a2be84dd5f2380b304db23f18
diff --git a/test/convolve_test.cc b/test/convolve_test.cc
index 1724db3..2e3659f 100644
--- a/test/convolve_test.cc
+++ b/test/convolve_test.cc
@@ -645,7 +645,7 @@
     make_tuple(64, 64, &convolve8_ssse3)));
 #endif
 
-#if HAVE_AVX2
+#if HAVE_AVX2 && HAVE_SSSE3
 const ConvolveFunctions convolve8_avx2(
     vp9_convolve8_horiz_avx2, vp9_convolve8_avg_horiz_ssse3,
     vp9_convolve8_vert_avx2, vp9_convolve8_avg_vert_ssse3,
@@ -665,7 +665,7 @@
     make_tuple(64, 32, &convolve8_avx2),
     make_tuple(32, 64, &convolve8_avx2),
     make_tuple(64, 64, &convolve8_avx2)));
-#endif
+#endif  // HAVE_AVX2 && HAVE_SSSE3
 
 #if HAVE_NEON_ASM
 const ConvolveFunctions convolve8_neon(