Fix Aapt so that duplicate package ID errors are not incorrectly reported.

Aapt falsely reports package ID conflicts unless base packages are included
in strictly ascending order based on their package IDs. This fix addresses
that issue while still detecting and reporting conflicts correctly when they
actually exist.

Change-Id: Ic8059b87f919641d086df88d1556f5fa0063739f
Merge "Fix Aapt so that duplicate package ID errors are not incorrectly reported." into kitkat