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.
Replace the use of the internal_report structure (for reports from
engines, MPV etc) with the Rose program interpreter.
SOM processing was reworked to use a new som_operation structure that is
embedded in the appropriate instructions.
Move report preconditions (bounds, exhaustion, etc) into program
instructions and use a more direct path to the user match callback than
the adaptor functions.
Report handling has been moved to new file src/report.h. Reporting from
EOD now uses the same instructions as normal report handling, rather
than its own.
Jump target tracking in rose_build_bytecode.cpp has been cleaned up.
