lib/string: use glibc version

the performance of memcpy and memmove of the general version is very
inefficient, this patch improved them.

Signed-off-by: Miao Xie <miaox*******>
adapted by faux123 for 3.0.13 kernel
Signed-off-by: Andrei F <luxneb@gmail.com>
sched: use cpu capacity to decide if a ILB is needed