THRIFT-2770 thrift.internal.traits unittest fails due to std.metastrings import
Client: D
Patch: David Nadlinger

This closes #237

I originally wrote what became std.traits.SetFunctionAttributes as thrift.internal.traits.ChangeFuncAttrs. Now that it has been in Phobos for a number of releases, remove the local copy. This is both a cleanup and fixes the -unittest build in 2.066, where std.metastrings (which was just a stray import anyway) has finally been removed.