eclass: pull in updates for newer EAPI

BUG=chromium:600061
TEST=`cbuildbot chromiumos-sdk` works
CQ-DEPEND=CL:336990

Change-Id: I267b129a2abe2a0bd490fdced9d87d0297b442fb
Reviewed-on: https://chromium-review.googlesource.com/336930
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: David Hendricks <dhendrix@chromium.org>
12 files changed