Optimize slub

Conflicts:
	mm/slub.c
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

Conflicts:
	lib/string.c