start well-known-names enum from 1 + pre-initialise keys_map with well-known-names

include/mapnik/json/json_grammar_config.hpp

@@ -34,10 +34,10 @@ namespace mapnik { namespace json {
 
 enum well_known_names
 {
-    type = 0,
-    geometry = 1,
-    coordinates = 2,
-    properties = 3
+    type = 1,
+    geometry,
+    coordinates,
+    properties
 };
 
 constexpr char const* wkn_to_string(well_known_names val)

utils/mapnik-index/process_geojson_file_x3.cpp

@@ -428,7 +428,14 @@ std::pair<bool,typename T::value_type::first_type> process_geojson_file_x3(T & b
     auto const* itr = start;
 
     extract_positions<base_iterator_type, boxes_type> callback(itr, boxes);
-    mapnik::json::grammar::keys_map keys;
+    mapnik::json::grammar::keys_map keys =
+        {
+            {"type", mapnik::json::well_known_names::type},
+            {"geometry", mapnik::json::well_known_names::geometry},
+            {"coordinates", mapnik::json::well_known_names::coordinates},
+            {"properties", mapnik::json::well_known_names::properties}
+        };
+
     std::size_t bracket_counter = 0;
     auto feature_collection_impl = x3::with<mapnik::json::grammar::bracket_tag>(std::ref(bracket_counter))
         [x3::with<mapnik::json::keys_tag>(std::ref(keys))