Revert "Revert "Use of ::= in the Compiler, eliminating almost all mutable state from its methods.""
Revert "Revert "Use of ::= in the Compiler, eliminating almost all mutable state from its methods.""

This reverts commit 81043353071213a2681f394451761a98737f60f5.

krfkeith/slate-language,briantrice/slate-language,krfkeith/slate-language,briantrice/slate-language,briantrice/slate-language,krfkeith/slate-language,krfkeith/slate-language,briantrice/slate-language,briantrice/slate-language,krfkeith/slate-language,briantrice/slate-language,krfkeith/slate-language