Build: suppress some warnings in Camlp4 syntax
Build: suppress some warnings in Camlp4 syntax

These are not being triggered in Travis at the moment, but they came up
during the Jenkins build. We should look into why Travis isn't building
the Camlp4 syntax in future work.

[skip ci]

rneswold/lwt,rneswold/lwt,ocsigen/lwt,ocsigen/lwt,ocsigen/lwt,rneswold/lwt,c-cube/lwt,c-cube/lwt,c-cube/lwt