* insns.def (opt_regexpmatch1): check Regexp#=~ is not defined before
  calling rb_reg_match()

* test/ruby/test_regexp.rb: add test

* vm.c (ruby_vm_redefined_flag): change type to short[]

* vm.c (vm_redefinition_check_flag): return REGEXP_REDEFINED_OP_FLAG if
  klass == rb_cRegexp

* vm.c (vm_init_redefined_flag): setup BOP flag for Regexp#=~

* vm_insnhelper.h: add REGEXP_REDEFINED_OP_FLAG

[ruby-core:57385] [Bug #8953]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43050 b2dd03c8-39d4-4d8f-98ff-823fe69b080e