Distinguish PHPDoc annotation arguments clearly

The PHPDoc annotations match the current line greedily. In addition to this making annotation arguments (e.g. type specifiers) blend in with the rest of the line it is inconsistent with any continuation lines, which take the default comment colour. This makes the PHPDoc matching a little more sophisticated, so annotation arguments and identifiers stand out.

Actual vs. expected:
![phpdocparam](https://cloud.githubusercontent.com/assets/603326/3258018/6c6ca48a-f234-11e3-88e0-1fd9d8a78190.png)

This can arguably be simplified. In particular, line 18 in the screenshot takes steps to render the commas as comments rather than part of the identifier or annotation name. Since it's insane to use commas in identifier names, that complexity may not be necessary. A similar case can be made for line 21.