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*******>
Signed-off-by: faux123 <reioux@gmail.com>
Merge branch 'lupus-cm-10.2' of github.com:garwedgess/android_kernel_samsung_smdk4412 into lupus-cm-10.2