nsf.c: - new cmd for debugging: nsf::__db_show_obj - added MethodDupInternalRep() and FlagDupInternalRep() since they appear to be required in Tcl 8.6b2.
nsf.c: - moved methodEpochCounters from global vars to the interp state to improve resue in multi threaded apps - separated objectMethodEpoch and instanceMethodEpoch - bump version number to 2.0a2