Rewrite module loading in order to be smaller

[bettio]

Module code loading / parsing is implemented in opcodesswitch.h when IMPL_CODE_LOADER is defined, that relies on the mega-switch and a lot on inlined code. As a consequence the compile code takes a lot of space. The whole functionality can be replaced with a smaller parsing loop that relies on some kind of opcode definition table, saving quite a lot of space on flash memory. Last but not least, a good smarter implementation, should verify consistency and avoid some issues, such as calling missing BIFs (it causes a crash).