Provide a minimal type for query_def.
Provide a minimal type for query_def.

query_def is specified across kv and repl, but the type no longer
exists, provided a minimal type to use for the meantime.  We can't use
typer to derive the type, because riak_index is so incorrectly
specified, typer believes all of the functions return no value.

andytill/riak_kv