call rb_frame_callee() only once

* eval_error.c (error_pos): no needs to call rb_frame_callee() twice.

* safe.c (rb_secure, rb_insecure_operation): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40918 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-05-25

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40919 b2dd03c8-39d4-4d8f-98ff-823fe69b080e