build: Remove unused constructs: `space' and `AC_PROG_MAKE_SET' The makefile variable `space' is never used. The autoconf output variable `SET_MAKE' is never used, so the autoconf macro `AC_PROG_MAKE_SET' has been removed.

open(IN,"<crypt.ind");
open(OUT,">crypt.ind.tmp");
$a = <IN>;
print OUT  "$a\n\\addcontentsline{toc}{chapter}{Index}\n";
while (<IN>) {
   print OUT $_;
}
close OUT;
close IN;
system("mv -f crypt.ind.tmp crypt.ind");