statement be a list of bare C strings, rather than String nodes, which is
what they need to be for copyfuncs/equalfuncs to work.  Fortunately these
node types never go out to disk (if they did, we'd likely have noticed the
problem sooner), so we can just fix it without creating a need for initdb.
This bug has been there since 8.0, but 8.3 exposes it in a more common
code path (Parse messages) than prior releases did.  Per bug #3940 from
Vladimir Kokovic.