More MONO_FORCE_COMPAT where it may be needed.

Index: external/corefx/src/Common/src/CoreLib/System/Collections/Generic/Dictionary.cs
--- external/corefx/src/Common/src/CoreLib/System/Collections/Generic/Dictionary.cs.orig
+++ external/corefx/src/Common/src/CoreLib/System/Collections/Generic/Dictionary.cs
@@ -1610,7 +1610,8 @@ namespace System.Collections.Generic
                 {
                     if (_version != _dictionary._version)
                     {
-                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                        if (Environment.GetEnvironmentVariable ("MONO_FORCE_COMPAT") == null)
+                            ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
                     }
 
                     while ((uint)_index < (uint)_dictionary._count)
