Update 67: Added macros to the code generator.

A new header file macros.h contains macros for chunks of code printed
by generate.c. This file is included by all generated header files.
Makes the code generator and the generated source files look a little
nicer.
Refactoring reference interpreter code.
Refactoring reference interpreter code (part 2)
Refactoring reference interpreter (part 3)

Also performed some regression testing. One bug was unearthed and fixed,
otherwise behaviour is equivalent to the non-refactored interpreter.
Merge remote-tracking branch 'github/master' into dev