configure: Include AVX availability in summary output.

configure

@@ -3100,6 +3100,7 @@ if enabled x86; then
     echo "3DNow! extended enabled   ${amd3dnowext-no}"
     echo "SSE enabled               ${sse-no}"
     echo "SSSE3 enabled             ${ssse3-no}"
+    echo "AVX enabled               ${avx-no}"
     echo "CMOV enabled              ${cmov-no}"
     echo "CMOV is fast              ${fast_cmov-no}"
     echo "EBX available             ${ebx_available-no}"