Update Chromium's copy of libjpeg-turbo to the latest upstream stable
release (v2.1.0) and re-apply our local changes documented in
README.chromium.

This upstream release fixes a long-standing libjpeg6b compatability
issue[1] meaning we can dispense with the locally-applied workaround.

[1] http://crbug.com/398235

Change-Id: Icae6741f49d4ae8bc12ccfcbef416fb6a6fa16f1