[csmith-project/creduce] 1f250b: added an option --check-reference=<val>

[Yang Chen <chenyang@cs.utah.edu>]

  Branch: refs/heads/master
  Home:   https://github.com/csmith-project/creduce
  Commit: 1f250b2055843ec186b8148f798d829501dc93fe
      https://github.com/csmith-project/creduce/commit/1f250b2055843ec186b8148f798d829501dc93fe
  Author: Yang Chen <chenyang@cs.utah.edu>
  Date:   2016-07-24 (Sun, 24 Jul 2016)

  Changed paths:
    M clang_delta/ClangDelta.cpp
    M clang_delta/ExpressionDetector.cpp
    M clang_delta/ExpressionDetector.h
    M clang_delta/Transformation.h
    M clang_delta/TransformationManager.cpp
    M clang_delta/TransformationManager.h

  Log Message:
  -----------
  added an option --check-reference=<val>

Passing --check-reference=<ref_val> to clang_delta will insert the
following code pattern for the expression candidate:

  __creduce_expr_tmp_1 = expr_candidate;
  if (__creduce_expr_tmp_1 != ref_val) abort();
  ...

Currently, this option only works with --expression-detector.