Build and use YASM

My testing doesn't show much difference, I will take Craig T's word for it :-)

Author: NigelPearson

OSX/build/osx-packager.pl

@@ -67,6 +67,7 @@
         'mysqlclient',
         #'dbus',
         'qt-4.6',
+        'yasm',
       ],
   'mythplugins'
   =>  [
@@ -257,7 +258,13 @@
   {
     'url'  => "$sourceforge/sourceforge/libexif/libexif-0.6.17.tar.bz2",
     'conf' => [ '--disable-docs' ]
-  }
+  },
+
+  'yasm' =>
+  {
+    'url'  => 'http://www.tortall.net/projects/yasm/releases/yasm-1.1.0.tar.gz',
+  },
+
 );