Patch for devpts support and backup toggling

Hi,

I made a patch (against QEmacs 0.3.1), to add the features mentioned in the topic.
I mailed Fabrice about it, but thought to post here too if someone would be interested.

Making backup files is toggled with 'make-backup-files', the command doesn't provide 
any minibuffer output, because I found it segfaulted when I tried to run it from my
configuration file, and haven't had time to look more deeply into it.

I added devpts support because I haven't got boxes with legacy PTYs, however the code
should and seems to work with legacy pty's, it uses a /dev/pty** node when i force it to.

This patch also fixes the configure script so that the quotation mark after QE_VERSION
in config.h isn't on a new line, because this broke compilation at least here.

The patch can be found at http://ecx.no-ip.org/misc/qemacs-0.3.1-aon1.patch

Regards,
Antti