[1/2] Speed up booting on multicore devices.

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

Change-Id: Id42b2bf4a737f93f9ecd9b5819344adbb735f0fb

Conflicts:
	services/java/com/android/server/pm/PackageManagerService.java
PackageManager: Fix concurrent access to shared state

Stop multiple threads from all calling add on the same HashMap.

Cleanup the use of a boolean flag by removing concurrent writes
to it.

Change-Id: I8d61fe7294dcb67ee7d0d7de88d90d2051c310e6