Add a string pool pointer to the feature; stop passing it as an arg

serial.cpp

@@ -17,6 +17,7 @@
 #include "options.hpp"
 #include "main.hpp"
 #include "pool.hpp"
+#include "memfile.hpp"
 #include "projection.hpp"
 #include "evaluator.hpp"
 #include "milo/dtoa_milo.h"
@@ -740,6 +741,8 @@ int serialize_feature(struct serialization_state *sst, serial_feature &sf) {
 		}
 	}
 
+	sf.stringpool = r->poolfile->map;
+
 	long long geomstart = r->geompos;
 	sf.geometry = scaled_geometry;
 	serialize_feature(r->geomfile, &sf, &r->geompos, sst->fname, SHIFT_RIGHT(*(sst->initial_x)), SHIFT_RIGHT(*(sst->initial_y)), false);