added.
* vm_insnhelper.h: ditto.
* variable.c (rb_const_get_0), insns.def: Constants should not be
cached if const_missing is called. [ruby-core:21059] [Bug #967]
* bootstraptest/test_class.rb: add a test.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@21536 b2dd03c8-39d4-4d8f-98ff-823fe69b080e