[Dillo-dev] include guard naming

I was just going through and changing the include guards that don't follow the dillo convention, and then I glanced at http://en.wikipedia.org/wiki/Include_guard and it reminds me that the C++ standard prohibits '_'s at the beginning. Does anyone care enough to have an opinion? If we want to rm the leading or surrounding underscores, I might as well do that too before committing. [pop/smtp isn't working at the moment, so I'm sending this through webmail. Let's hope they doesn't mangle line wrapping or anything.]