lib/string: use glibc version

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

Change-Id: I8dc171a0326af57ed4ff77b1f7826c9ff91921f8
rwsem: squashed rwsem: steal writing sem for better performance  rwsem-spinlock: let rwsem write lock stealable

Change-Id: I6b1fa8a987cf95418f8f4f97e94159cafc5c4d9b