* Asterisks are now treated (styled) as valid tag characters.
* The vertical pipe | and tilde ~ are now treated as selector characters.
(CSS namespace selector, and preceding element selector, respectively.)
* Pseudo-classes can be extended with additional simple selectors. (Not
sure if extending pseudo-elements in the same way is necessary. The CSS
specs don't seem to indicate this kind of usage with pseudo-elements.)
Useful for pseudo-classes like :not() and [to lesser extent] :lang(), but
also for some vendor-specific pseudo-classes.

Friedrich Vedder.
- Improve support for context style diffs (add new style SCE_DIFF_CHANGED
for changed lines).
- Improve support for diff's generated by Subversion.
- Fix styling and folding for lines containing chunk dividers ("---").