* ext/dl/lib/dl/import.rb (DL::Importer#extern): adds filename and
  line number to module_eval'ing for readability of backtrace.
  (DL::Importer#bind): ditto.

* ext/dl/lib/dl/struct.rb (DL::CStructBuilder#create): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@21137 b2dd03c8-39d4-4d8f-98ff-823fe69b080e