prevent raw_post_data parsing on defined view functions

[hugo]

There should be a way to prevent parsing of POST data for some view functions. This would be usefull for example for view functions that do their own POST parsing, like some view function that parses XMLRPC requests or some other special format. Currently access to POST (either the dict as a whole or some variable in it) will instantiate the QueryDict for the post data and so parse the post raw data - even if it isn't a valid POST query string. That would put high load on the machine if the POST data is rather large - think of a XMLRPC API where ImageField content is transported as base64 data ...