application:set_env's 4th argument has now changed, and takes a property
list.  Adapt existing code to detect the Erlang version, and make the
appropriate call.

Correctly type the prepare_index_query function.

For some reason, Dialyzer believes that the caller to this function will
only be undefined or {_, _}, but it's unclear where this assumption is
coming from; the caller of this function comes in through a coverage
query through riak_core, so dialyzer is deriving this call from some
unknown place.

Ignore the warnings for the time being.

Ignore the warnings that say the function isn't typed correctly; the
type signatures for each function are correct.