fix default build when getpass() is unavailable if the system doesn't support getpass, we still default on the options that require it which causes a build failure. instead, only default enable these when getpass is available.

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");