More style fixes.
improved Vim coding guidelines checker

* Avoids highlighting some matches when inside C++ comments
* Add operators << and >>
* Automatic initialization when opening Vim in the Haiku source
directory (if you use the same directory layout as me)
* Matches are highlighted in red, rather than reusing the "Search" match
group. You can pick another color by editing the "highlight Style"
definition.

Improvements are still welcome.