Test for joining a list of path fragments starting with an empty string.
Fix File::join when the first path fragment is an empty string.
Create directories with correct permissions in Dir::mkdir.
Much improved File::join implementation.
Protect against recursive arrays in File::join.
No need to import RubyError here.
Merge branch 'master' into jerith/dir-file-fixes
Better dir permissions test.
Untag core/file/join specs.
Put recursion_guard in a more sensible place.
recursion_guard improvements.
ExecutionContext test.
Fix recursive array error message.
Merge pull request #382 from jerith/jerith/dir-file-fixes

Dir::mkdir and File::join fixes