Fixes for recent commits

The Makefile.example file now has the ALT_OBJ and ALT_TARGET (with a
comment explaining how to use it) and the alt rule (which if the
variables are left empty it will do nothing with 'make alt' or 'make
everything').

The example Makefile now has the everything rule as well, for those who
have an alt target.

Fix links to next/try.sh, next/try.alt.sh and next/Makefile.example in
html files (guidelines/rules/FAQ) to not link to GitHub as they're
supposed to be downloaded.

next/Makefile.example

@@ -130,6 +130,16 @@ endif
 PROG= prog
 OBJ= ${PROG}.o
 TARGET= ${PROG}
+# If you have alternate code, try something like:
+# ALT_OBJ= ${PROG}.alt.o
+# ALT_TARGET= ${PROG}.alt
+#
+# or so.
+#
+# Please remove these lines either way.
+#
+ALT_OBJ=
+ALT_TARGET=
 
 # list any data files supplied with the submission
 #
@@ -150,11 +160,27 @@ all: data ${TARGET}
 ${PROG}: ${PROG}.c
 	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
 
+# alternative executable
+#
+alt: data ${ALT_TARGET}
+	@${TRUE}
+
+${PROG}.alt: ${PROG}.alt.c
+	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
+
+
+
 # data files
 #
 data: ${DATA}
 	@${TRUE}
 
+# both all and alt
+#
+everything: all alt
+	@${TRUE}
+
+
 # one suggested way to run the program
 #
 try: ${PROG} ${DATA}