SPRINGFIELD — Republican Gov. Bruce Rauner has used campaign dollars, the courts and the bully pulpit to fight public unions during his short time in office.Late last week he wielded another weapon, the veto pen, to try to limit their influence. On Friday, Rauner insisted lawmakers alter a bill aimed at raising wages for public works laborers and giving unions more control over how much they’re paid.In his veto message he said the legislation, Senate Bill 2964, “does not meet constitutional standards and …