fix Makefile and README.md for 2015/burton

2015/burton/Makefile

@@ -102,8 +102,8 @@ CINCLUDE=
 #CINCLUDE= -include stdlib.h
 #CINCLUDE= -include stdio.h
 #CINCLUDE= -include stdlib.h -include stdio.h
-#CINCLUDE= -I ${X11_INCDIR}
-#CINCLUDE= -I ${HOMEBREW_PREFIX}/include/SDL2
+#CINCLUDE= -I ${X11_INCDIR} -I ${X11_INCDIR}/X11
+#CINCLUDE= `${SDL2_CONFIG} --cflags`
 
 # Optimization
 #
@@ -188,14 +188,14 @@ all: data ${TARGET}
 ${PROG}: ${PROG}.c
 	${CC} ${CFLAGS} $< -o $@ ${LIBS}
 
-${PROG}.alt: ${PROG}.alt.c
-	${CC} ${CFLAGS} $< -o $@ ${LIBS}
-
 # alternative executable
 #
 alt: data ${ALT_TARGET}
 	@${TRUE}
 
+${PROG}.alt: ${PROG}.alt.c
+	${CC} ${CFLAGS} $< -o $@ ${LIBS}
+
 # data files
 #
 data: ${DATA}