o the initial comment is wrong: creating messages is already
	  implemented

	o Message.getbodytext: if the mail or it's part contains an
	  empty content-transfer-encoding header, the code used to
	  break; the change below treats an empty encoding value the same
	  as the other types that do not need decoding

	o SubMessage.getbodytext was missing the decode argument; the
	  change below adds it; I also made it unconditionally return
	  the raw text if decoding was not desired, because my own
	  routines needed that (and it was easier than rewriting my
	  own routines ;-)