send-email: teach sanitize_address to do rfc2047 quoting

send-email: teach sanitize_address to do rfc2047 quoting

Without this patch I'm not able to properly send emails as I have a
non-ascii character in my name.

I removed the _rfc822 suffix from the function name as it now does more
than rfc822 quoting.

I dug through rfc822 to do the double quoting right.  Only if that is not
possible rfc2047 quoting is applied.

Signed-off-by: Uwe Kleine-K\e,Av\e(Bnig <ukleinek@informatik.uni-freiburg.de>
Cc: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>