feat(misc): various misc fixes/enhancement

fix(Tigrisl): use repr to escape filepath on windows

feat(FFI): added FFI instructions/gadgets

Merge branch 'cwc' into pratt

Merge branch 'pratt' into cwc

feat(new IR): closure conversion

feat(PP): pretty print values;

perf(env): replace hash-based structures with tree-based, more suitable
for modifying shared (RC > 1) environments

fix(Typing): regression that undefined rectypes being able to

elide mutual block

threading support for evaluation

refactor(parsing): cut path;

feat(mutual rectype): add support for mutual rectype