add more detail to the doc comment

add more detail to the doc comment

	* libsoup/soup-session.c (soup_session_cancel_message): add more
	detail to the doc comment

	* libsoup/soup-message.c (SoupMessage): Note in the doc comment
	that reason phrases are not very useful, and should not be
	presented to the user.

	* libsoup/soup-status.c: add a comment explaining why reason
	phrases aren't localized. Also some misc doc fixes.
	(soup_status_get_phrase): Note in the doc comment that you
	shouldn't present reason phrases to the user.

svn path=/trunk/; revision=1248