Added mention of type alias use/restrictions.

docs/Version2Changes.md

@@ -97,7 +97,8 @@ modules like this:
             anotherInternalConstant = 0x66
     externalConstant=0x77
 
-Whenever names might be ambiguous, they can be disambiguated with the `::` syntax (using a qualified import using "as"):
+Whenever names might be ambiguous, they can be disambiguated with the
+`::` syntax (using a qualified import using "as"):
 
     import ExternalModule as eModule
     ...
@@ -172,6 +173,13 @@ This can help break the Catch-22 situation that sometimes arises when you're
 writing a function that needs access to type variables, but you're not yet sure
 about the whole function's type signature.
 
+Type Aliases
+------------
+
+Type aliases are only permitted to be defined on curried primitive
+types in Cryptol version 2.  In Cryptol version 1, for example, tuples
+were permitted in type declaration contexts.
+
 Type Classes
 ------------