* gc.c: use gc_verify_internal_consistency() instead of
  gc_check_before_marks_i() for check consistency
  on RGENGC_CHECK_MODE >= 2.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44231 b2dd03c8-39d4-4d8f-98ff-823fe69b080e