#139 Return raw post data as istream

[Sebastian Schaffert]

In some webservices it would be very useful to return the raw post data as an istream that can be read as-needed instead of keeping the complete post data in memory. This would allow to keep much tighter control over memory consumption, regardless of the size of a post request.

[Artyom Beilis]

Implemented in CppCMS 1.2 as filtering: http://cppcms.com/wikipp/en/page/cppcms_1_2_filtering