CherryPy Patch: allow UTF-8 encoding of headers.

Modern browsers can use non standardized UTF-8 encoding on headers,  most notably the Content-Disposition.
In Content-Disposition it is used to carry file names.
Patch CherryPy so that UTF-8 is tried before ISO-8859-1.
Allow for weird encoding of names of uploaded NZB files.

Sometimes CherryPy returns correct Unicode, sometimes UTF-8 disguised as Unicode.