[cmp] Add AlternativesNumeberVector Pass

This pass insert a vector into the module that contains the number of
alternatives available for each instruction. This vector will be used
inside a loop that select the alternative that will be executed for
each instruction during the run.

This commit contains also InstructionAlternativesUtils. This file
contains the table (instruction, alternativesNumber) and a
metafunction that is used to generate the alternatives number vector.