The std::vector argument to addMetaEvent should be const.

[dewhisna]

The version of the addMetaEvent function that takes the metaData as a std::vector type should accept that std::vector argument as a const type. Otherwise, callers of this function that pass data from constant member functions and/or retrieve their data from constant getter functions have to either do a const_cast or declare their own types mutable and/or add temporary variables of a non-const type when they shouldn't need to.