New version of my bytes patch:
 - fix IMAP4_stream: use subprocess.Popen() as my previous 
imap_stream.patch but use bytes instead of characters
 - fix IMAP4_SSL: sslobj wasn't set in IMAP4_SSL.open() but used, for 
example, in read() method; remove duplicate method (simplify the code)
 - IMAP4.read(): call file.read() multiple times if the result is 
smaller than size (needed especially for the SSL version); FIXME: does 
this function raise an error of EOF or just loop forever? should we 
stop the loop if data is b''?