[csmith-project/creduce] 4200a1: passes now have the option to return ERROR when so...

[John Regehr <regehr@cs.utah.edu>]

  Branch: refs/heads/master
  Home:   https://github.com/csmith-project/creduce
  Commit: 4200a1b494b503da304345ac0eb567ca39d4ee45
      https://github.com/csmith-project/creduce/commit/4200a1b494b503da304345ac0eb567ca39d4ee45
  Author: John Regehr <regehr@cs.utah.edu>
  Date:   2015-11-09 (Mon, 09 Nov 2015)

  Changed paths:
    M clex/driver.c
    M creduce/creduce.in
    M creduce/creduce_utils.pm
    M creduce/pass_clang.pm
    M creduce/pass_clang_binsrch.pm
    M creduce/pass_clex.pm
    M creduce/pass_comments.pm

  Log Message:
  -----------
  passes now have the option to return ERROR when something goes wrong

add an option to kill c-reduce when a pass returns ERROR and actually
do this when any pass except those that invoke clang_delta do that

refactor error codes of clex a bit