hashtest: fix build so the suite actually runs

htest.c was missing the "typedef struct hash hash" that hash.h
requires, and the Makefile linked the top-level ../hash.o which is
built without -DHASH_DEBUG, leaving hash_dump/hash_item_print
undefined. Build a local hash.o with the flag instead. All 16 tests
now compile and pass.

hashtest/Makefile

@@ -1,6 +1,9 @@
 
 CFLAGS=-DHASH_DEBUG -O2 -Wall
-OBJ=../hash.o ../gap.o htest.o
+OBJ=hash.o ../gap.o htest.o
+
+hash.o: ../hash.c
+	$(CC) $(CFLAGS) -c -o $@ $<
 
 htest: $(OBJ)
 	$(CC) -o htest $(OBJ)

hashtest/htest.c

@@ -29,6 +29,7 @@ struct hash_item {
 };
 
 typedef struct hash_item* hash_item;
+typedef struct hash hash;
 
 #include "../hash.h"