Add missing 1994/shapiro/shapiro.alt.c

With a tip from Leo the missing alt code has been added to the website.

Ta, Leo (🦁⭐️🌌)!

1994/shapiro/Makefile

@@ -118,8 +118,8 @@ OBJ= ${PROG}.o
 DATA= shapiro.md
 TARGET= ${PROG}
 #
-ALT_OBJ=
-ALT_TARGET=
+ALT_OBJ= ${PROG}.alt.o
+ALT_TARGET= ${PROG}.alt
 
 
 #################
@@ -146,6 +146,10 @@ ${PROG}_t1: ${PROG}.c
 alt: data ${ALT_TARGET}
 	@${TRUE}
 
+
+${PROG}.alt: ${PROG}.alt.c
+	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
+
 # data files
 #
 data: ${DATA}