[boost] [parameter] Fixing links

The attached patch fixes a few of links in the parameter documentation. But there's still a problem because in the following lines 'tag::name' and 'tag::index' are misinterpreted as links in the generated documentation. parameter::parameters< required<tag::name, is_convertible<_,char const*> > , optional<tag::index, is_convertible<_,int> >

const spec;

Daniel