* 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.rb

@@ -0,0 +1,27 @@
+require 'fiddle.so'
+require 'fiddle/function'
+require 'fiddle/closure'
+require 'dl'
+
+module Fiddle
+  Pointer = DL::CPtr
+
+  if WINDOWS
+    def self.win32_last_error
+      Thread.current[:__FIDDLE_WIN32_LAST_ERROR__]
+    end
+
+    def self.win32_last_error= error
+      Thread.current[:__FIDDLE_WIN32_LAST_ERROR__] = error
+    end
+  end
+
+  def self.last_error
+    Thread.current[:__FIDDLE_LAST_ERROR__]
+  end
+
+  def self.last_error= error
+    Thread.current[:__DL2_LAST_ERROR__] = error
+    Thread.current[:__FIDDLE_LAST_ERROR__] = error
+  end
+end