[ASan] Remove the replace_cfallocator flag, which is used no more.
See https://code.google.com/p/address-sanitizer/issues/detail?id=10 for the context.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@174629 91177308-0d34-0410-b5e6-96231b3b80d8