Add namespace handling in attribute values

Previously, you could only reference namespace prefixes in attribute names:

<View xmlns:appcompat="http://schemas.android.com/apk/res/android.support.v7.appcompat"
      appcompat:name="hey"
      ...

Now you can also reference them in resource names within an attribute value:

      ...
      android:text="@appcompat:string/confirm"
      ...

Which will be treated as "@android.support.v7.appcompat:string/confirm".

Change-Id: Ib076e867a990c80cf877a704eb77cd1ef0b23b52
diff --git a/tools/aapt2/Resource.h b/tools/aapt2/Resource.h
index f928acd..31104fbe 100644
--- a/tools/aapt2/Resource.h
+++ b/tools/aapt2/Resource.h
@@ -130,6 +130,7 @@
     uint8_t typeId() const;
     uint16_t entryId() const;
     bool operator<(const ResourceId& rhs) const;
+    bool operator==(const ResourceId& rhs) const;
 };
 
 //
@@ -178,6 +179,10 @@
     return id < rhs.id;
 }
 
+inline bool ResourceId::operator==(const ResourceId& rhs) const {
+    return id == rhs.id;
+}
+
 inline ::std::ostream& operator<<(::std::ostream& out,
         const ResourceId& resId) {
     std::ios_base::fmtflags oldFlags = out.flags();