Decoding support added when replying or forwarding message.

Decoding support added when replying or forwarding message.
Original patch was provided by Viktor S. Grishchenko <gritzko@plotinka.ru>
Currently patch works only with utf-8 translations and with Ukrainian/Bulgarian
translations if message has similar charset. Patch should not have any
effect on other translations and From: and Subject: headers still need to be
fixed with some messages.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@5829 7612ce4b-ef26-0410-bec9-ea0150e637f0