Here we have *real* interning, producing unique references if and only if the input is unique! Boy am I glad I invested time into this, because it's really fun to work with.
Hopefully my logic regarding Send-ness and Sync-ness aren't completely unsound.
- StringArena provides an arena for immutable strings, inspired by other string interners, and keeps track of the ends of every allocated string. Strings inserted into the arena are assigned a Symbol.
- intern::Interner keeps track of the hashes of each inserted string, and provides deduplication for interned strings. This allows referential comparison between interned strings
- global_intern::GlobalSym provides metered access to a Global Interner, and has a Display implementation which queries the Interner.
The global interner is planned for use in cl-ast.
TODO: the unstable raw_entry API is about to be removed from Rust. Maybe switch to hashbrown, or write my own hash table?
