Revert "lib/string: use glibc version"

This reverts commit 9f4e0fbda5fb4292d998c3cd7ce371a1a55913df.
Revert "lib/memcopy: use glibc version"

This reverts commit 831ee755dc8248600b559c6c65e047de5ccf6f35.
GPU OC: more clean up work