new macro to check if a URI is a valid http or https URI.
* libsoup/soup-uri.h (SOUP_URI_VALID_FOR_HTTP): new macro to check
if a URI is a valid http or https URI.
* libsoup/soup-uri.c (soup_uri_new_with_base): Update http/https
check to use SOUP_URI_VALID_FOR_HTTP().
* libsoup/soup-session.c (redirect_handler): Check
SOUP_URI_VALID_FOR_HTTP() and call it an error if the check fails.
* libsoup/soup-message.c (soup_message_new): Remove the uri->host
check from here. Update docs to clarify that @uri must be an
http/https URI.
(soup_message_new_from_uri): Check SOUP_URI_VALID_FOR_HTTP().
Update docs.
(soup_message_set_uri): Check SOUP_URI_VALID_FOR_HTTP(). Update
docs.
Should prevent the crash in #528882, but there's still something
going wrong there at a higher level.
svn path=/trunk/; revision=1155