[PECOFF] Print a better error message for unknown module-definition file directive.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@199018 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Add a helper function to read an integer from .def file.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@199019 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Support NAME directive.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@199020 91177308-0d34-0410-b5e6-96231b3b80d8