New client and server API tutorials.

New client and server API tutorials.

	* docs/reference/client-howto.xml:
	* docs/reference/server-howto.xml: New client and server API
	tutorials.

	* docs/reference/*: reorganize, regenerate, fill in some missing
	pieces, etc

	* libsoup/soup-connection.c (soup_connection_new): document the
	varargs param

	* libsoup/soup-date.h: sync prototypes to declarations for gtk-doc.

	* libsoup/soup-headers.c (soup_headers_parse_response): fix typo
	in doc.