The old .bat file wasn't working for reasons that are unclear, and
which it did not seem worth the trouble to ascertain.
The new perl script has been tested and is known to work.
Soon it will be tested regularly on the buildfarm.
The .bat file is kept as a simple wrapper for the perl script.
src/pl/plpgsql/src/plerrcodes.h, src/include/utils/errcodes.h, and a
big chunk of errcodes.sgml are now automatically generated from a single
file, src/backend/utils/errcodes.txt.
Jan Urbański, reviewed by Tom Lane.