* config/x86/x86_avx.cc: Remove #undef __AVX__ hack.  Tidy comments.
        * Makefile.am (x86_avx.lo): Only add -mavx if ARCH_X86_AVX.
        * configure.ac (ARCH_X86_AVX): New conditional.
        * Makefile.in, configure: Rebuild.

From-SVN: r181261