Cleanup #7865
Updated by Loïc Dachary about 10 years ago
make use of "ifunc":http://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Function-Attributes.html#index-g_t_0040code_007bifunc_007d-attribute-2529 to chose the function depending on CPU features
http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/i386-and-x86-64-Options.html#i386-and-x86-64-Options
"discussion":http://www.spinics.net/lists/ceph-devel/msg18451.html