Gov. Bruce Rauner has blocked a measure that would tighten rules on the use of jailhouse informants.The Republican governor last week vetoed a bill that would require prosecutors in certain cases to disclose informants’ backgrounds, their evidence against the accused and any deals they struck with the state at least 30 days prior to the relevant hearing or trial.Such rules have applied in Illinois capital cases since November 2003 with such disclosures required to be made in a “timely” manner during …