[xml] Error handling on a per-parser base

[Ralf Mattes <rm mh-freiburg de>]

Hello list,

is it possible to register a custom error function per xmlParserCtxtPtr
created by xmlCreatePushParserCtxt? I'd like to parse documents in 
parallel and would need error reporting per parser context. Dispatching
on user_data in the error callback seems inside out.

TIA Ralf Mattes