* 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/extconf.rb

@@ -0,0 +1,23 @@
+require 'mkmf'
+
+# :stopdoc:
+
+dir_config 'libffi'
+
+unless have_header('ffi.h')
+  if have_header('ffi/ffi.h')
+    $defs.push(format('-DUSE_HEADER_HACKS'))
+  else
+    abort "ffi.h is missing. Please install libffi."
+  end
+end
+
+unless have_library('ffi')
+  abort "libffi is missing. Please install libffi."
+end
+
+have_header 'sys/mman.h'
+
+create_makefile 'fiddle'
+
+# :startdoc: