Fix #8427: Promoted typeError to fatalTypeError in ReferencesResolver::endVisit(UserDefinedTypeName).

test/libsolidity/syntaxTests/structs/member_type_eq_name.sol

@@ -0,0 +1,7 @@
+contract C {
+  struct S {t t;}
+  function f(function(S memory) external) public {}
+}
+// ----
+// TypeError: (25-26): Name has to refer to a struct, enum or contract.
+// TypeError: (53-61): Internal type cannot be used for external function type.

test/libsolidity/syntaxTests/structs/member_type_func.sol

@@ -0,0 +1,8 @@
+contract C {
+  function f() public {}
+  struct S {f x;}
+  function g(function(S memory) external) public {}
+}
+// ----
+// TypeError: (50-51): Name has to refer to a struct, enum or contract.
+// TypeError: (78-86): Internal type cannot be used for external function type.