remove unused 'mustquote' regex

We set an imapobj.mustquote which apparently was used in previous
incarnations of imaplib or imaplib2, however, nothing in our codebase
makes use of that. So let us remove it.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/imaplibutil.py

@@ -284,8 +284,6 @@ class WrappedIMAP4(UsefulIMAPMixIn, IMAP4):
         # imaplib2 uses this to poll()
         self.read_fd = self.sock.fileno()
 
-mustquote = re.compile(r"[^\w!#$%&'+,.:;<=>?^`|~-]")
-
 def Internaldate2epoch(resp):
     """Convert IMAP4 INTERNALDATE to UT.
 

offlineimap/imapserver.py

@@ -212,8 +212,6 @@ class IMAPServer:
                     imapobj = imaplibutil.WrappedIMAP4(self.hostname, self.port,
                                                        timeout=socket.getdefaulttimeout())
 
-                imapobj.mustquote = imaplibutil.mustquote
-
                 if not self.tunnel:
                     try:
                         # Try GSSAPI and continue if it fails