This patch adds replay.json file. It will be
used for adding record/replay-related data structures and commands.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <160174519444.12451.3472949430004845434.stgit@pasha-ThinkPad-X280>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>