Ignore all warnings in generate riak_core_pb

Because tools.mk performs a simple grep filter using the patterns in
dialyzer.ignore-warnings, simply using the module name is enough to make it
ignore all warnings in that module. This should be a time saver
Merge pull request #997 from basho/feature/ignore-all-riak-core-pb-warnings

Ignore all warnings in generated riak_core_pb

Reviewed-by: lordnull