Speed up booting on multicore devices [2/2]

1. Add multithreading support to Installer/installd.
2. Parallelize package scanning.
3. Parallelize boot dexopt.

Change-Id: I13630de9d75d13c0368d261b3564b787067b65b1
Merge branch 'du44' of https://github.com/DirtyUnicorns-KitKat/frameworks_native into HEAD