Sema: Fix validateDeclForNameLookup() to use the right flags when resolving type alias underlying type

Otherwise, we would in some cases reject this idiom, which looks odd
at first glance but we do support and users rely on:

struct Generic<T> {}

protocol P {
  typealias X = Generic
  // Equivalent to 'typealias X<T> = Generic<T>'
}

Author: slavapestov

lib/Sema/TypeCheckDecl.cpp

@@ -7924,8 +7924,10 @@ void TypeChecker::validateDeclForNameLookup(ValueDecl *D) {
         validateAccessControl(typealias);
 
         ProtocolRequirementTypeResolver resolver;
+        TypeResolutionOptions options =
+          TypeResolutionFlags::TypeAliasUnderlyingType;
         if (validateType(typealias->getUnderlyingTypeLoc(),
-                         typealias, TypeResolutionOptions(), &resolver)) {
+                         typealias, options, &resolver)) {
           typealias->setInvalid();
           typealias->getUnderlyingTypeLoc().setInvalidType(Context);
         }

test/decl/typealias/protocol.swift

@@ -290,3 +290,12 @@ struct Y11: P11 { }
 extension P11 {
   func foo(_: X11<Self.A>) { }
 }
+
+// Ordering issue
+struct SomeConformingType : UnboundGenericAliasProto {
+  func f(_: G<Int>) {}
+}
+
+protocol UnboundGenericAliasProto {
+  typealias G = X
+}