envutil.rb: using caller_locations
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38375 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
envutil.rb: using caller_locations
take file and line by using caller_locations if not given.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38375 b2dd03c8-39d4-4d8f-98ff-823fe69b080e