Merged r10812 from trunk (#12375)

fix receiving mail subject broken which does not begin with encoding name.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/branches/2.1-stable@10816 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/mail_handler.rb

@@ -373,7 +373,8 @@ class MailHandler < ActionMailer::Base
       # try to reencode to utf8 manually with ruby1.8
       begin
         if h = email.header[:subject]
-          if m = h.value.match(/^=\?([^\?]+)\?/)
+          # http://tools.ietf.org/html/rfc2047#section-4
+          if m = h.value.match(/=\?([^\?]+)\?[BbQq]\?/)
             subject = Redmine::CodesetUtil.to_utf8(subject, m[1])
           end
         end