This commit replaces the ue2::unordered_{set,map} types with their STL
versions, with some new hashing utilities in util/hash.h. The new types
ue2_unordered_set<T> and ue2_unordered_map<Key, T> default to using the
ue2_hasher.
The header util/ue2_containers.h has been removed, and the flat_set/map
containers moved to util/flat_containers.h.
- Change the compile of literal matchers to two passes.
- Reverse the bucket assignment in FDR, bucket with longer literals has
smaller bucket id.
- Squash the buckets of included literals and jump to the the program of
included literals directly from parent literal program without going
through FDR confirm for included iterals.
