179 skip fchmod flag (#1)

[dsingh-mw]

Added test for the flag "ignore_attribute_errors"

[Lastique]

I don't think there's a good way to test this. Replacing fchmod (a) requires relying on specific linker behavior, (b) may affect code other than boost::filesystem::copy_file and (c) relies on that copy_file actually uses fchmod internally. Neither of these I like, so I'm not going to merge this.