Add "-lz" to link line to get in zlib.

Not all Linux distributions seem to need it (notably not YDL on ppc64), but
enough ones obviously do.

Makefile

@@ -8,7 +8,7 @@ all: $(PROG)
 install: $(PROG)
 	install $(PROG) $(HOME)/bin/
 
-LIBS= -lssl
+LIBS= -lssl -lz
 
 init-db: init-db.o