PathArrayness::TrieNode currently uses std::unordered_map to store child nodes. stdx::unordered_map is preferred, but has compilation issues on Windows variants due to the windows compiler's stricter rules about when forward declarations for a class can be used (in this case, TrieNode contains a member map _children of TrieNode objects, which the windows compiler does not allow when the map is of type std::unordered_map). This could potentially be solved by storing a unique pointer to TrieNode instead of the object itself.

This change would need to be benchmarked for performance and compared to the baseline established here.