Patches: many fixes related to bodystruct stuff

[José Dapena Paz <jdapena igalia com>]

	Hi,

	This is a patches series for bodystruct implementation.


	* On getting the decoded stream from bs mime part, reset
	to offer a stream started in 0 offset.
	* Fix error detecting embedded message/rfc822 in bs.
	* Add the bodystruct of the child to the embedded message created
	in tny_camel_bs_mime_part_get_parts, as this is the expected
	structure in tinymail.
	* Handle better in IMAP "NIL" parameter in fetch response.
	* Fix part specs of direct child of attached messages in
	bodystruct parser.
	* Refactor decode_it and decode_it_2 in _tny_camel_decode_raw_header
	* Decode properly headers in TnyCamelBsMsgHeader, to return utf8
	strings.
	* Fix decoding of rfc2047 strings in utf8 in some cases.


-- 
José Dapena Paz <jdapena igalia com>
Igalia