Improve how to redefine sleep in 1993/rince

Using a Makefile variable one can now do just

    make clobber SLEEP=18 alt

or whatever number they wish.

Also added jkb.alt and jkb.alt2 rules that correspond to the jkb rule.

1993/rince/Makefile

@@ -58,7 +58,7 @@ ARCH=
 
 # Defines that are needed to compile
 #
-CDEFINE= -DZ=17
+CDEFINE= -DZ=${SLEEP}
 
 # Include files that are needed to compile
 #
@@ -143,6 +143,24 @@ jkb: ${PROG}
 alt: data ${ALT_TARGET}
 	@${TRUE}
 
+# variable to control how long to sleep in alt version
+SLEEP= 17
+
+${PROG}.alt: ${PROG}.alt.c
+	${CC} ${CFLAGS} -DZ=${SLEEP} $< -o $@ ${LDFLAGS}
+
+${PROG}.alt2: ${PROG}.alt2.c
+	${CC} ${CFLAGS} -DZ=${SLEEP} $< -o $@ ${LDFLAGS}
+
+jkb.alt: ${PROG}.alt
+	${RM} -f $@
+	${LN} $< $@
+
+jkb.alt2: ${PROG}.alt
+	${RM} -f $@
+	${LN} $< $@
+
+
 # data files
 #
 data: ${DATA}