comment on constants on mlvm/constants.ml
comment on constants on mlvm/constants.ml

Signed-off-by: Matthias Goergens <bc66cfc3364dde487c6cd1d5e0a8c91a454ed3da@citrix.com>

djs55/forkexecd,xapi-project/message-switch,johnelse/forkexecd,xapi-project/message-switch,xapi-project/message-switch