sys-fs/exfat-utils: import 1.2.6 from upstream

This CL imports exfat-utils 1.2.6 from upstream Gentoo to replace the
older version of exfat-utils in chromiumos-overlay. The EAPI is
downgraded from 6 to 5 in the ebuild.

BUG=chromium:723102
CQ-DEPEND=CL:505941
CQ-DEPEND=CL:505942
TEST=Tested the following:
1. `emerge-$BOARD exfat-utils`
2. Run platform_CrosDisksFilesystem test.
3. Insert an exFAT formatted USB drive and verify read/write operations
   on the drive via File.app.

Change-Id: I8e05fb2309673e5cabab87fadb00f5b86ca9c1c2
Reviewed-on: https://chromium-review.googlesource.com/506329
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
(cherry picked from commit becc6270f5b623ff6ed00d8ae52950f55011b2cd)
Reviewed-on: https://chromium-review.googlesource.com/513031
Commit-Queue: Ben Chan <benchan@chromium.org>
3 files changed