po: Update English (US) translation

[Frédéric Delanoy]

On Tue, Oct 18, 2011 at 17:01, Francois Gouget <fgouget at free.fr> wrote:
> My understanding it that en.po contains the British translation and is
> treated as just another translation. So instead of containing just the
> strings that need to be different, all the other strings are copied as
> well by the translators so they know what has been checked already.

For clarity, we should probably have no en_US.po but only en.po (and
possibly other en_XX.po like en_GB.po)
maybe a soft link from en_US.po to en.po to make it clear)

The current situation (en.po and en_US.po) makes it look like en_US.po
is an "adapted" version of "standard" en.po (which is then presumably
en_GB), as is e.g. fr_CA vs fr.po

This is not the first time someone adapts the en_US.po IIRC.

Frédéric