Support for multi-domain functions

Hello,

I am working on integrating rails engines with fast_gettext and I would like to have two additional set of gettext functions:

1) d_(domain, string) that would accept domain via first parameter. I know one can do this via local thread variables, but there are places (e.g. in rails views) where this is much better.

2) ad_(string) that would do the translation across all domains until translation is found.

I am working on these two sets of new gettext functions - would you like this contribution upstream?