Since the initialization of the pointer happens across the libc library boundry
MSAN will not know the pointer was initialized. This fixes MSAN failures in
test/strings/string.conversions.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@222052 91177308-0d34-0410-b5e6-96231b3b80d8