mailhandler 6.x-1.6

Changes since DRUPAL-6--1-5:

• Initialize the node object with default values (see http://drupal.org/node/334775)
• Removed debugging messages that shouldn't have been there from the start
• "From header: Sender" doesn't seem to work for listserv mails #292163: "From header: Sender" doesn't seem to work for listserv mails
• By anoopjohn: Fix "Bad message number on retrieval" message on certain occasions #349141: Bad message number on retrieval
• by mfb: add some default values, to avoid php errors #300389: Fix some PHP notices on mailbox administrative interface.
• By mfb: try decoding before deciding a mail part is text #346080: Text parts not decoded
• Append revision id to nodes being updated by mailhandler #448592: "This content has been modified by another user, changes cannot be saved."