Add alt code to 2004/gavare

On the author's web page for the entry
(https://gavare.se/ioccc/ioccc_gavare.c.html) they provided an
unobfuscated version of the code. The code has been added to the repo
and Makefile as well.

To compile use:

     make alt

and use gavare.r3 as you would use gavare.

2004/gavare/Makefile

@@ -114,8 +114,8 @@ OBJ= ${PROG}.o
 DATA=
 TARGET= ${PROG}
 #
-ALT_OBJ=
-ALT_TARGET=
+ALT_OBJ= ${PROG}.r3.o
+ALT_TARGET= ${PROG}.r3
 
 
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