Lower types for SILDeclRefs from the interface types of their referents, dragging the old type along for the ride so we can still offer the context to clients that haven't been weaned off of it. Make SILFunctionType's interface types and generic signature independent arguments of its Derive the context types of SILFunctionType from the interface types, instead of the other way around. Do a bunch of annoying inseparable work in the AST and IRGen to accommodate the switchover.
Swift SVN r12536
Thanks to the way we've set up our diagnostics engine, there's not actually
a reason for /everything/ to get rebuilt when /one/ diagnostic changes.
I've split them up into five categories for now: Parse, Sema, SIL, IRGen,
and Frontend, plus a set of "Common" diagnostics that are used in multiple
areas of the compiler. We can massage this later.
No functionality change, but should speed up compile times!
Swift SVN r12438
