automake po / pot file integration: first tests available

[Bruno Haible]

Hi Ralf,

I've pushed on the 'pot-primary' branch most of the planned tests. 4 tests to
go, still. But with this, you can now start working on the implementation.

Of course, the tests are untested, so they likely contain a number of stupid
small mistakes. But they also contain a lot of nifty small details that are
intended as written.

Bruno