Structured Parcelables: int/string default values.

Initial two types for defaults.

Syntax is:
parcelable MyParcelable {
    String name = "wicked";
    int rest = 0;
}

Bug: 110758329
Test: runtests.sh
Change-Id: Ieadf503ccb9acedf6782c15964c2d4957549542d
diff --git a/aidl.cpp b/aidl.cpp
index f859b1d..d8cc4b8 100644
--- a/aidl.cpp
+++ b/aidl.cpp
@@ -171,6 +171,10 @@
                 TypeNamespace* types) {
   int err = 0;
   for (const auto& v : parcel->GetFields()) {
+    if (!v->CheckValid()) {
+      err = 1;
+    }
+
     if (!types->MaybeAddContainerType(v->GetType())) {
       err = 1;  // return type is invalid
     }