SEA IR type handling complete for fibonacci.

types.h: Encapsulated types map into separate class.
code_gen.*, visitor.h: Added visitor function for
         unnamed constants to enable correct
         .dot display and type handling.
type_inference_visitor.cc: Propagated types through
             phi functions, invoke, add-int instructions. Added
             SEA IR type merging functions.

Change-Id: I0fb1c4d40e3af43dc295133a826ce125a787cc33