add a new generic auth callback that can be used with any subclass to do

add a new generic auth callback that can be used with any subclass to do

	* libsoup/soup-auth-domain.c
	(soup_auth_domain_set_generic_auth_callback):
	(soup_auth_domain_check_password): add a new generic auth callback
	that can be used with any subclass to do cleartext password
	checking against messages. Suggested by Mathias Hasselmann.

	* libsoup/soup-auth-domain-basic.c: Implement generic auth

	* libsoup/soup-auth-domain-digest.c: Implement generic auth.
	(soup_auth_domain_digest_evil_check_password): Gone, use the
	generic version now.

svn path=/trunk/; revision=1048