HTML highlighter: unknown token classes now yield a CSS class with that name instead of :error
A new Ruby test

A bunch of new tests. Delphi and XML are now tested, too.
bench/example.dump deleted (depends on Ruby version, OS, whatever. Nothing for the repo.)

Test case added.

Adjusted gem.rake.

HTML scanner fixed.
Enhanced filetype.rb: .rake files, xml, yaml (preparing for YAML scanner.)
Enhanced test/ruby/1.in.rb.
Added XML scanner with example.

plugin.rb: made all_plugin_names public.

ROADMAP and TODO updated.

Ruby scanner:
Fixed a bug: Fancy strings don't allow \w delimiters.
They _do_ also allow whitespace delimiters, but adding this would cause
many scan errors. So I leave this bug unfixed.

CSS style changes/enhancments (mainly the new background color for inline code, affects all Ruby code.)
Demos and tests adjusted.

Plugin: new PluginHost::default method.

Scanner:
- New setup method
- ability to re-use a scanner
- ability to keep the tokens
- minor changes to token caching and string flattening

Encoder: Error if token content is neither String nor Symbol.

HTML encoder:
- more warnings for unclosed tokens
- output now UTF-8

Ruby Scanner:
- bug: symbols before => now do not include =; {:foo=>bar} is valid Ruby code
- try to close all open tokens
- constants now all with specific namespace (for speed, I hope)

Styles: new :entity/en class.

Test suite now gives hinted HTML output.