Bump to mono/2017-12/15d76bf5 (#1377)

jonpryor · jonpryor · commit ae08bb28d7e3 · 2018-03-07T12:03:35.000-05:00
Context: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/569184 Context: mono/mono#7338 Context: xamarin/maccore#629 Fixes decoding of CMS/PKCS #7 messages with an explicit cryptographic object identifier.
diff --git a/external/mono b/external/mono
@@ -1 +1 @@
-Subproject commit 607cbde47a19c361c73ab2598e325d656805ac8f
+Subproject commit 15d76bf5e2d174ac4a01e70fdf130e8b4565a602
