Fix make clobber in 2018/burton1

When scripthd was renamed to scripthd.sh the DATA field should have been
updated to have scripthd.sh. Also make clobber should remove scripthd
(but not scripthd.sh).

Updated .gitignore.

2018/burton1/.gitignore

@@ -7,3 +7,4 @@ indent.o
 prog
 prog.alt
 prog.orig
+scripthd

2018/burton1/Makefile

@@ -111,7 +111,7 @@ PROG= prog
 #
 OBJ= ${PROG}.o
 CSRC= ${PROG}.o
-DATA= scripthd
+DATA= scripthd.sh
 TARGET= ${PROG}
 #
 ALT_OBJ= ${PROG}.alt.o
@@ -206,7 +206,7 @@ clean:
 	fi
 
 clobber: clean
-	${RM} -f ${TARGET} ${ALT_TARGET}
+	${RM} -f ${TARGET} ${ALT_TARGET} scripthd
 	${RM} -rf *.dSYM
 	@-if [ -e sandwich ]; then \
 	    ${RM} -f sandwich; \