Architecture for Scheme interpreter linking

[hawkw]

There needs to be some way for the Scheme interpreter to link in other Scheme files. This is necessary to write any kind of non-trivial programs.

I'd also like it if there was a way to link in compiled Seax bytecode files for performance reasons. This makes it so you don't have to re-interpret the standard library every time you want to map or reduce over something, or whatever.

This should also talk with the FFI at the bytecode level if I want to write Scheme programs that use libc.

[hawkw]

I have no idea how this will work, as I've never actually had the opportunity to write a linker before. @janyljumadinova can probably offer some advice.

[hawkw]

Changed the title to disambiguate between this and #19, which it depends on.