Bump min Xamarin Studio version to latest alpha. (#38)

To get a version of mdtool that works without any Xamarin.Mac
licenses.

Also bump maccore to run the mmp regression tests now that
we have a working Xamarin Studio.

commit xamarin/maccore@9a5e6f02f305d1b580229b37c7775c4897738f4d
Author: Rolf Bjarne Kvinge <rolf@xamarin.com>
Date:   Tue May 10 18:20:48 2016 +0200

    [tests] There is now a released version of Xamarin Studio whose mdtool doesn't care about the XM license, so we can run the mmp regression tests again.

Make.config

@@ -58,8 +58,8 @@ MAX_MONO_VERSION=4.4.99
 MIN_MONO_URL=http://download.mono-project.com/archive/4.0.4/macos-10-x86/MonoFramework-MDK-4.0.4.4.macos10.xamarin.x86.pkg
 
 # Minimum Xamarin Studio version
-MIN_XAMARIN_STUDIO_URL=http://download.xamarin.com/studio/Mac/XamarinStudio-5.10.3.51-0.dmg
-MIN_XAMARIN_STUDIO_VERSION=5.10.3.51
+MIN_XAMARIN_STUDIO_URL=https://files.xamarin.com/~rolf/XamarinStudio-6.0.0.5104-0-1.dmg
+MIN_XAMARIN_STUDIO_VERSION=6.0.0.5104
 MAX_XAMARIN_STUDIO_VERSION=6.1.0.9999
 
 # Minimum OSX versions

mk/xamarin.mk

@@ -1,5 +1,5 @@
 ifdef ENABLE_XAMARIN
-NEEDED_MACCORE_VERSION := 8cc7ade11c50a815393788f7fe417223f69bdaf7
+NEEDED_MACCORE_VERSION := 9a5e6f02f305d1b580229b37c7775c4897738f4d
 NEEDED_MACCORE_BRANCH := master
 
 MACCORE_DIRECTORY := maccore