IDL-to-C++11 v1.6

[jwillemsen]

• Add support for @optional
• Extend support for the new type traits for bitmask

Specification: https://www.omg.org/spec/CPP11/1.6
Issues fixed in v1.6: https://issues.omg.org/issues/spec/CPP11/1.6/fixed

[jwillemsen]

Support for the new IDL to C++11 type traits for bitmask has been added to the prototype.

[jwillemsen]

First code to support @optional annotation on https://github.com/jwillemsen/taox11/tree/jwi-idl4optional