Provide a link to Boost.Context's stack_traits documentation to look up
is_unbounded(), minimum_size() and maximum_size().
Fix spellings of minimum_size() and maximum_size().
When stack_traits::is_unbounded(), we shouldn't have to care about
stack_traits::maximum_size(). Consistently change:
! traits_type::is_unbounded() && size <= traits_type::maximum_size()
to:
traits_type::is_unbounded() || size <= traits_type::maximum_size()