[xml] error handling with xmlreader

[Baurzhan Ismagulov <ibr radix50 net>]

Hello,

I'm defining my own ErrorFunc for xmlreader. This works fine, however
the messages contain newlines. I don't have a terminal and send
everything to syslog, where newlines look not so good. Does it make
sense to patch libxml2 to print newlines inside the default ErrorFunc
and not in the caller?

Another question. I'd like to print my own error messages with
information like filename, line number etc. Is there something like
xmlTextReaderGetLocator? For now, I declared struct xmlTextReader in my
sources and get ctxt from it, but I would prefer to have an "official"
wrapper in xmlreader.h.

Thanks in advance,
Baurzhan.