asn2wrs: support for (SIZE(A..B),...) constraint

Change-Id: Icf4c6c7c91cbdc22aff2363b0d21b24d123da482
Reviewed-on: https://code.wireshark.org/review/37824
Reviewed-by: Pascal Quantin <pascal@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

tools/asn2wrs.py

@@ -3511,6 +3511,7 @@ class Constraint (Node):
         if self.IsSize():
             if self.type == 'Size':
                 (minv, maxv, ext) = self.subtype.GetValue(ectx)
+                ext = ext or (hasattr(self, 'ext') and self.ext)
             elif self.type == 'Intersection':
                 if self.subtype[0].IsSize() and not self.subtype[1].IsSize():
                     (minv, maxv, ext) = self.subtype[0].GetSize(ectx)