Add benchmark for sorting function.

bench/Makefile

@@ -109,6 +109,7 @@ bench-collectionc0:
 	@./bench-collectionc.exe 30
 	@./bench-collectionc.exe 40
 	@./bench-collectionc.exe 41
+	@./bench-collectionc.exe 50
 
 bench-plain:
 	$(CC) $(CFLAGS) $(CPPFLAGS) bench-plain-c.c -o bench-plain-c.exe