This step builds on Lang Hames work to change Archive::child_iterator
for better interoperation with Error/Expected. Building on that it is now
possible to return an error message when the size field of an archive
contains non-decimal characters.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276025 91177308-0d34-0410-b5e6-96231b3b80d8