Better C++ regex

Based upon this comment: https://github.com/github/linguist/issues/1626#issuecomment-66371622
*sighs* I feared that might happen.. only thing we can do for the time being is anchor to the start of the line and add a skip for white-space only. this will still match under certain conditions even when it shouldn't but without teaching linguist how to scan comments to exclude them it's the best we can do.