Remove unneeded constructor.
Use the interpreter to handle expressions where the function is actually a
function-valued expression.  The previous code lacked proper GC protection.
Minor code cleanup.
Add makefile target for a human-readable version of the runtime LLVM IR.
Force exception handling symbols to be included in the runtime bytecode by
generating code that uses them, instead of just declaring them.

Declaring the symbols isn't sufficient, as clang removes unused symbols when
optimization is enabled.