imported/implemented boost/serialization/variant now contains code for serialization of boost::variant, boost::variant2 and std::variant. Care has been taken to depend only on the public interfaces of these types. Hence, it is reasonable to hope that the archives are compatible in that one type could be saved and subsequently loaded into a compatible type. Hopefully this will be useful in some way. At a minimum it minimizes code duplication.
a) eliminate warning on narrowing of int to char in unescape
b) eliminate warning on cast of version types
c) fix error which appears when serializing collections of boost::variant
2. created copy of original throw exception for use in the serialization Library.vcproj
3. addressed error maintenance of static type table which shows up on GCC
4. fixed internal names in xml_grammar so as not to conflict with likely preprocessor macros.
5. streamlined xml_grammar so as not to depend upon on non-thread safe component.
[SVN r48575]
