CPP1117 — Improve bitmask mapping

The bitmask mapping is very basic, it doesn't give any type safety or more modern API. The spec should be improved, the <X>Bits type should be removed, only one type should be used. Also when there are multiple bitmasks with the same bitfield name they could result in a name clash. Maybe map to a enum class and add the operators ~,|,^,& for the enum class as inline operations to modify the enum class as a bitmask. At that moment the Bit type can be removed.

When time permits I will make a proof of concept for TAOX11

Defer breaking change to the bitmask mapping

The existing mapping in IDL-to-C++11 is based on DDS XTypes where it has been in a formal standard for a number of years.
There are certainly reasons to have a mapping that makes better use of the C++ type system, but this would come at a cost in terms of divergence from OMG precedent.