[boost] Boost.Parser need final approval

I've *finally* gotten back around to making Boost.Parser properly ready for bringing into the next Boost release. Marshall suggested I post here to make sure that people who participated in the review have a chance to check that the notes from the review all got fixed/implemented. So, this is that email. Please have a look if you get the chance. The issue tracker for the github project is down to 8 items, all of which are nice-to-haves. All the issues raised during the review were captured in the issues list, and taken care of. Zach