Documentation/releases: Add release notes

Documentation/releases: Add release notes

This adds the release notes for all of our old releases that have notes
to the documentation directory.  The release notes for the next release,
4.9 is added here as well.

I would request that people document their changes for the next release
themselves if they wish them to be in the release notes.

Change-Id: I7440a3130f2f7d80c4434d2b5a918e62bbd08fbb
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/26799
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>