fix alt rules in Makefiles

For Makefiles that have alt related rules, moved
the related rules under the alt rule section.

In some cases where there is no alt code,
removed alt rules and/or targets.

2018/bellard/Makefile

@@ -125,8 +125,8 @@ OBJ= ${PROG}.o
 DATA= fruits.bin lena512.bin vintage_cars.bin Lenna.png
 TARGET= ${PROG}
 #
-ALT_OBJ= ${PROG}.alt.o
-ALT_TARGET= ${PROG}.alt
+ALT_OBJ=
+ALT_TARGET=
 
 
 #################
@@ -143,9 +143,6 @@ 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}