SMTP 8BITMIME compliance

Currently, K-9 Mail detects if an SMTP server supports 8BITMIME (RFC
6152), and if so, TextBody parts are sent with content-transfer-ecoding =
8bit.  Otherwise, they are sent using quoted-printable.

This adds the required "BODY=8BITMIME" parameter to the MAIL command when
sending messages to servers that support 8BITMIME.

src/com/fsck/k9/mail/transport/SmtpTransport.java

@@ -490,8 +490,8 @@ public class SmtpTransport extends Transport {
 
         Address[] from = message.getFrom();
         try {
-            //TODO: Add BODY=8BITMIME parameter if appropriate?
-            executeSimpleCommand("MAIL FROM:" + "<" + from[0].getAddress() + ">");
+            executeSimpleCommand("MAIL FROM:" + "<" + from[0].getAddress() + ">"
+                    + (m8bitEncodingAllowed ? " BODY=8BITMIME" : null));
             for (String address : addresses) {
                 executeSimpleCommand("RCPT TO:" + "<" + address + ">");
             }