* ext/fiddle/*: Adding fiddle library to wrap libffi

* test/fiddle/*: testing fiddle extension
* ext/dl/lib/dl.rb: Requiring fiddle if it is available
* ext/dl/lib/dl/callback.rb: using Fiddle if it is available
* ext/dl/lib/dl/func.rb: ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27640 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/fiddle/lib/fiddle/closure.rb

@@ -0,0 +1,17 @@
+module Fiddle
+  class Closure
+    attr_reader :ctype
+    attr_reader :args
+
+    class BlockCaller < Fiddle::Closure
+      def initialize ctype, args, abi = Fiddle::Function::DEFAULT, &block
+        super(ctype, args, abi)
+        @block = block
+      end
+
+      def call *args
+        @block.call(*args)
+      end
+    end
+  end
+end

ext/fiddle/lib/fiddle/function.rb

@@ -0,0 +1,5 @@
+module Fiddle
+  class Function
+    attr_reader :abi
+  end
+end