don't allow Module::Install::Admin::copy to mangle newlines

This pull request updates `Module::Install::Admin::copy()` to treat all data as binary, which prevents the introduction of windows newlines when doing `make dist` on a windows system. It comes with a test.

The second commit of this PR updates the filehandling to lexical filehandles and 3-arg open. That's optional and for your benefit if you like it.