gettext markup of library sources

[Benjamin Kosnik]

I realize now that Phil actually read the messages documentation before
posting the patch. Sorry about that.

>This file gets included in every single standard  header.  The macro
>gettext_noop is in direct contradiction with our current policy of not
>hijacking user's name space when we're implementing internal helpers.

Yes. I thought Phil had already made that clear. That part of the patch
isn't needed at the moment anyway, and should just not be checked in.
Perhaps Phil can post a revised patch if you think it would clarify the
issue. 

The only part used at the moment is the '_(x)' define. That's the part that
should go in.

Really, I feel like this patch was preliminary and posted for discussion
only anyway. 

One related thing might be to think about standardizing the
exception.what() messages. With 

__throw_out_of_range("bitset -- set() argument too large");

maybe going to something like

__throw_out_of_range("bitset::set argument too large");

Too bad there isn't a exception.where() function... anyway. It might be
nice to have consistent exception strings.

Thoughts?

-benjamin