[libvirt] Adding timestamps for all emulator output

Hello, I think it would be useful if libvirt will be able to prefix all messages from emulator pipes with the date stamping, for example I am trying to catch very rare and non-fatal race with virtio-serial-bus: Guest failure in adding device virtio-serial0.0 which is specific to the Windows guests on qemu-kvm. I have supporting infrastructure which can tell me exact times for every action upon this VM, but as bug is not frequent, the continuous monitoring looks like an overkill for a desired goal - find a correlation between emulator event and message from stderr. Patching emulator itself is barely an option, as it is ugly, requires refresh of the running code via loopback migration and completely non-universal, as every hypervisor should be modified seperately. I`d highly appreciate positive consideration for such functionality addition or can write a patch shortly, if needed. Thanks!