Add AutoNSDMI experimental option turned on by default
Allow parsing of 'auto' or decltype(auto) as an NSDMI
Support simple (non-this capturing lambdas) deduction of 'auto' nsdmi's
  - in ParseLexedMemberInitializer - deduce auto NSDMI's in the order they were declared.

Lambda's capturing 'this' still requires some work.
The sizeof the containing class seems to be correctly calculated - i need to figure out exactly how that is happening.