change next_block condition from <255 to <nb_block

common-c-code/common_flight_plan.c

generated/CommonFP.v

src/semantics/FPBigStep.v

src/semantics/FPBigStepExtended.v

src/semantics/FPBigStepSized.v

src/verification/CommonFPVerification.v

src/verification/VerifFPToFPE.v