Fixes for C++98
Rename set() to assign() Will avoid ambiguity when ConcurrentSets are added to Junction, and more consistent with C++17's insert_or_assign.
Rename insert() to set() to avoid confusion with std::map::insert() std::map::insert() will only store the value if the key doesn't already exist. junction::ConcurrentMap_xxx::set() stores the value unconditionally.
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Initial commit