Mirror in object mode. Works like Mirror in edit mode but only works on local axis...

Mirror in object mode. Works like Mirror in edit mode but only works on local axis (doing it differently would require a much more clever algorithm).
Mirror Object is assigned to Ctrl-M and I've add Ctrl-M to call Mirror Edit (on top of M alone) for practical reason. We should consider switching both to Ctrl-M for pratical reasons but I kept M for backward compatibility
Also added the menu and toolbox counterparts.

Minor addition to arithb.c: A function to print vectors to the console. Easier for debuging.