Performance drop; need symbol table

[JoshDreamland]

Performance is looking pretty terrible. The more academic approach to lexing is partially responsible, but the core issue is that COW strings are gone. We're now SSO, which means we're copying variable names and chunks of code everywhere. Things that used to be efficient by-value are now terrible. So, thanks, Google.

JDI needs to incorporate a proper symbol table to deal with that. We can just store everything in it, honestly; doc comments, too, as needed.

Some of the macro application logic is particularly egregious as it hybridizes the string copy performance hit with dropping the optimizations that made the code difficult to maintain.