Silence compile time deprecated type warning

In Erlang >= 17.0 the type of dicts should be dict:dict/0
or dict:dict/2. But that's not compatible with Erlang R16.
Hence set a compile flag to silence it.

The warning with Erlang 17.0 is:

    gc-couchbase/src/spatial_view.erl:166: Warning: type dict/0 is
    deprecated and will be removed in OTP 18.0; use use dict:dict/0
    or preferably dict:dict/2

Change-Id: Ibee2cf50172e5aebd1636744ee491bc044724e8d
Reviewed-on: http://review.couchbase.org/41765
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Tested-by: Volker Mische <volker.mische@gmail.com>