Add character recoding utility functions
Simplify MessageBuffer

- Add implicit conversion from CharBuffer to MessageBuffer
- Don't use special overflow exception object
urlinfo: default: Big HTML fix/refactor

For dumb/obsolete sites only:
    We want to stop parsing as soon as we find both title and charset so don't
    rely on HtmlParser charset decoding. It probably wouldn't even work as
    desired in streaming mode (i.e. when breaking after title).