Add support for ALU operations on several cycles.
Merge branch 'jonathan' ; add unit tests.

Conflicts:
	cpu/alu.ml
Unsigned multiplication works (uses as many cycles as necessary) ; unit tests.
Correction de li pour valeurs négatives ; utilisation de labels dans des data.
Merge branch 'emile'
Better handling of unit tests.
Presentation... ie. nothing.
implemented a buggy division algorithm