Add jpeg_skip_scanlines() API to libjpeg-turbo

Add jpeg_skip_scanlines() API to libjpeg-turbo

jpeg_skip_scanlines() API, a subset decoding optimization
aimed at Android, was submitted upstream r1582. Pull that
change, and sundry fixes, into the Chromium repo.

This new API is targetted at Android devices, not Chrome,
and should have no affect on JPEG decode behavior or perf
of Chrome.

Chrome uses suspending data source JPEG decoding, and the
new API does not support such sources. Adding support for
suspending data sources is a future TODO, should the need
arise (refer to skbug.com/4036).

BUG=515694
BUG=468914
patch from issue 256280043 at patchset 50001 (http://crrev.com/256280043#ps50001)

R=agable@chromium.org

Committed: https://chromium.googlesource.com/chromium/deps/libjpeg_turbo/+/c9c8755c326b42c8d0dc938ec3f0d1d648bd361a

[agable, 2015-08-03 16:17:06]

agable@chromium.org changed reviewers:
+ agable@chromium.org, noel@chromium.org

[agable, 2015-08-03 16:17:07]

LGTM because Noel already gave LGTM on the prior issue on the other Rietveld
instance.

[agable, 2015-08-03 16:33:14]

Matt can't land this because this repo has no CQ and he is not yet a full
committer. Attempting to land on his behalf.

[agable, 2015-08-03 16:34:36]

Committed patchset #1 (id:1) manually as
c9c8755c326b42c8d0dc938ec3f0d1d648bd361a (presubmit successful).