[SimplifyLibCalls] Add noalias from known callsites

Summary:
Should be fine for memcpy, strcpy, strncpy.


Reviewers: jdoerfert, efriedma

Reviewed By: jdoerfert

Subscribers: uenoku, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66135

llvm-svn: 368724