[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

Patchset: 7
http://review.cyanogenmod.org/#/c/59909/
Fix build

Change-Id: I2764ec94ae8f4055f325ef4817043a991a206d56