Add css support for text-decoration-line

[lukeluluke]

No description provided.

[ezyang]

The rule here is accidentally correct (because we're still on the HTML 4 definition of text-decoration) but not semantically correct for CSS3, where text-decoration-line is a subset of text-decoration functionality. It would be better to give it a separate class (although it's probably easiest to just do an Enum). Also, this new rule needs a test.

[Rah1x]

@ezyang
Do you mean the following?

$this->info['text-decoration-line'] = new HTMLPurifier_AttrDef_Enum(
    ['none', 'underline', 'overline', 'line-through']
);

Let me know if you are happy with this, I will create a new PR and also add a test.

[ezyang]

Yup plz do

[Rah1x]

Done. have a look:
#360

[Rah1x]

since this is now completed via #360, we can delete this PR.