Bump to mono/2017-04/4498dc4a (#638)

jonpryor · jonpryor · commit 89bfebd8376e · 2017-06-08T08:28:25.000-04:00
Context: https://bugzilla.xamarin.com/show_bug.cgi?id=55603 Context: https://bugzilla.xamarin.com/show_bug.cgi?id=56821
diff --git a/external/mono b/external/mono
@@ -1 +1 @@
-Subproject commit 1a227379203671064ef08aa062af5e5c606d0ec9
+Subproject commit 4498dc4a62fe7dcd4e3b29898144f41d6396f577
