* ext/dl/lib/dl/func.rb (DL::Function#call): check tainted when
  $SAFE > 0.
* ext/fiddle/function.c (function_call): check tainted when $SAFE > 0.
* test/fiddle/test_func.rb (module Fiddle): add test for above.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40728 b2dd03c8-39d4-4d8f-98ff-823fe69b080e