Fix make clobber in 1998/schweikh3

Needs to remove samefile.alt.

Updated .gitignore too.

1998/schweikh3/.gitignore

@@ -10,6 +10,7 @@ indent.c
 indent.o
 prog.orig
 samefile
+samefile.alt
 schweikh3
 schweikh3.alt
 schweikh3.orig

1998/schweikh3/Makefile

@@ -211,7 +211,7 @@ clean:
 	fi
 
 clobber: clean
-	${RM} -f ${TARGET} ${ALT_TARGET}
+	${RM} -f ${TARGET} ${ALT_TARGET} samefile.alt
 	${RM} -rf *.dSYM
 	@-if [ -e sandwich ]; then \
 	    ${RM} -f sandwich; \