sub buildfile {
	my($filename)=shift;

	local $/;
	open(IN, "<$filename.in") or die "Can't open $filename.in: $!";
	my $text=<IN>;
	close(IN) or die "Can't close $filename.in: $!";

	$text =~ s/\$\{(\w+)\}/$c{$1}/g;
	$filename =~ s/_/./;	#config_h => config.h

	open(OUT, ">$filename") or die "Can't open $filename: $!";
	print OUT $text;
	close(OUT) or die "Can't close $filename: $!";
}