Return an ErrorOr<Binary *> from createBinary.

I did write a version returning ErrorOr<OwningPtr<Binary> >, but it is too
cumbersome to use without std::move. I will keep the patch locally and submit
when we switch to c++11.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199326 91177308-0d34-0410-b5e6-96231b3b80d8