Automatically generate the IR for the runtime module at compile time using
clang.
Refactoring.  Move the functions that generate code into a compiler class and ad
a CompilerContext class to hold any configuration settings or state that the
compiler cares about.
Reduce the amount of memory leaks in the JIT code.
Optimized local symbol lookups.

In order to lookup symbols efficiently, we use a frame whose layout is
determined at JIT compilation time.  The code that evaluates symbols then takes
advantage of that information when consulting the local frame.
Rename files to better match their contents.
Fix incorrect capitalization of 'BuiltInFunction'.