1.4 branch and master don't mvn compile

Possibly due to the use of the keywords 'false' and 'true' https://github.com/basho/riak_pb/blob/a7dec4960eceaa94699180bf8da8acf376f58d19/src/riak.proto#L120 and https://github.com/basho/riak_pb/blob/a7dec4960eceaa94699180bf8da8acf376f58d19/src/riak.proto#L123