Fix aapt -G to properly support class attr in fragment.

The code added attributes android:name and class to a
KeyedVector under the same key (fragment) so the 2nd
add (android:name) removed class with was never checked.

This replace the value type in the KeyedVector to be
Vector<NamespaceAttributePair> instead of just
NamespaceAttributePair.

Change-Id: I009b8a8cca878191661c2a63bb14c967d230498d