Support OTP release 18.x long_schedules

OTP Release 18 supports long GC schedules, like releases 16 and 17. Add
the needed configuration to rebar.config to tell the toolchain that it can
set the correct define-macro.

rebar.config

@@ -1,8 +1,9 @@
 {erl_opts, [debug_info,
             fail_on_warning,
             {platform_define, "^[0-9]+", namespaced_types},
-            {platform_define, "R16B01|R16B02|17", long_schedule},
+            {platform_define, "R16B01|R16B02|R16B03|R16B03-117|18", long_schedule},
             {parse_transform, lager_transform}]}.
+
 {eunit_opts, [verbose]}.
 {deps, [
         {cuttlefish, ".*", {git, "git://github.com/basho/cuttlefish.git", {tag, "2.0.1"}}}