I'm testing a Cache scheme that allows us to cache individual Decls. The idea is that when we transpile we cache most of the compiled Decls to be used on the next build. Since it looks the decl up with a unique full name (I still need to filter out non-unique names that might occur) this will pick out the decls on creating. If a decl isn't defined, then it is generated. The ast.Files for the sources are also cached so that type checking and instantiation of generics still work as before.

It may be possible in the future to add templated/stencil decls for generics but for now we can skip caching decls for specific decls, specifically those which came from generics definitions.