Implement the HTML serialization algorithm
Allow dropping the DOCTYPE during parse

And use this to reproduce the output of validator.nu's HTML2HTML.
Tokenizer debug cleanup
Keep parsing after </script> even though we don't handle it properly
Return to the correct raw data state after seeing a less-than sign

We were erroneously interpreting character references inside <script> in some cases.
Fix generate_implied_end_except and use it in one additional place
Implement <li> <dd> <dt>
InTable mode
InTableText mode
InCaption mode
InColumnGroup mode
Define a helper for inserting phantom elements
InTableBody mode
Simplify the use of declare_tag_set!()
InRow mode
InCell mode
Fix off-by-one in pop_until()
Add a debug helper
InSelect and InSelectInTable modes
More error messages