adb: implement compression for file sync.

This improves performance when syncing by up to 2x (remote cuttlefish
goes from 11.9 MB/s to 21.3 MB/s, blueline over USB 2.0 from 36 MB/s
to 70 MB/s).

This results in a slight drop in push speeds over USB 3.0 (125 -> 115
MB/s on blueline), presumably because we're compressing and extracting
on only a single thread, but the gains over lower bandwidth transports
make this worth it to submit this now and parallelize later.

Bug: https://issuetracker.google.com/150827486
Test: ADB_COMPRESSION={0, 1} test_device.py (with new/old adbd)
Change-Id: Ic2a0c974f1b6efecda115f87d336e3caac810035