doc: CodeMirror should ignore 'static/'self

[adrientetar]

CodeMirror JS syntax highlight currently trys to parse 'static or 'self blocks as string, and fails with a red error highlight because it doesn't find the end '.
We need to configure CodeMirror to ignore syntaxhighlight when it encounters these keywords.
See here: http://static.rust-lang.org/doc/0.8/rust.html#static-items

cc @marijnh

[adrientetar]

For reference, a cheap fix that didn't work: adrientetar@ded910f#diff-0

[marijnh]

The CodeMirror Rust mode is waaaay old and hasn't been updated in ages. I unfortunately don't have time for a rewrite right now (mostly because that'd first require familiarizing myself with modern Rust syntax, which'd take some time), but if someone decides to work on this, feel free to ask questions here, I'll try to answer.