AAPT2: Fix overlay support

Supports the <add-resource> tag and mimics old AAPT behavior of
not allowing new resources defined unless <add-resource> was used
or --auto-add-overlay was specified.

Change-Id: I9b461137357617ade37fd7045b418b8e6450b9c4
diff --git a/tools/aapt2/ResourceParser.h b/tools/aapt2/ResourceParser.h
index 1150758..04db577 100644
--- a/tools/aapt2/ResourceParser.h
+++ b/tools/aapt2/ResourceParser.h
@@ -83,7 +83,9 @@
     bool parsePrimitive(xml::XmlPullParser* parser, ParsedResource* outResource);
     bool parsePublic(xml::XmlPullParser* parser, ParsedResource* outResource);
     bool parsePublicGroup(xml::XmlPullParser* parser, ParsedResource* outResource);
+    bool parseSymbolImpl(xml::XmlPullParser* parser, ParsedResource* outResource);
     bool parseSymbol(xml::XmlPullParser* parser, ParsedResource* outResource);
+    bool parseAddResource(xml::XmlPullParser* parser, ParsedResource* outResource);
     bool parseAttr(xml::XmlPullParser* parser, ParsedResource* outResource);
     bool parseAttrImpl(xml::XmlPullParser* parser, ParsedResource* outResource, bool weak);
     Maybe<Attribute::Symbol> parseEnumOrFlagItem(xml::XmlPullParser* parser,