fast_xs provides C extensions for escaping text.
The original String#fast_xs method is based on the xchar code by Sam Ruby:
_why also packages an older version with Hpricot (patches submitted).
The version here should be compatible with the latest version of Hpricot
Ruby on Rails will automatically use String#fast_xs from either Hpricot
or this gem version with the bundled Builder package.
String#fast_xs is an almost exact translation of Sam Ruby's original
implementation (String#to_xs), but it does escape """ (which is an
optional, but all parsers are able ot handle it. XML::Builder as
packaged in Rails 2.0 will be automatically use String#fast_xs instead
of String#to_xs available.