replay: vmstate for replay module

This patch introduces vmstate for replay data structures.
It allows saving and loading vmstate while replaying.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20160926080810.6992.68420.stgit@PASHA-ISP>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>