Working ISO 2022 output function. Outputs full ISO 2022 (not sure

Working ISO 2022 output function. Outputs full ISO 2022 (not sure
what that's useful for but it seemed a pity not to do it) and
compound text.

I've completely removed the compound text implementation from
iso2022s.c in favour of using the more flexible iso2022.c, meaning
we can cope with nastiness such as DOCS.

This is largely untested: I've checked it on small examples as I
went along, but it lacks anything resembling a proper test suite.

git-svn-id: svn://svn.tartarus.org/sgt/charset@6378 cda61777-01e9-0310-a592-d414129be87e