[web] Fix HEAD request handling (closes #3677949) Don't special-case HEAD in CubicWebRequestBase.is_client_cache_valid so we don't return garbage. HEAD is supposed to return the actual headers that a GET would return, which we can't do if we bypass all the normal cubicweb logic. In particular, we no longer always return 200, and return the right Content-Length/Content-Type/...

[wsgi] avoid reading the entire request body in memory Import POST form handling code from https://raw.github.com/defnull/multipart/master/multipart.py to avoid reading arbitrary amounts of data from the network in memory. NOTES: - In the twisted case we limit the max request content-length to 100MB (by default), which seems kind of arbitrary, but avoids this issue - werkzeug.formparser has suitable code as well, but I don't know if we want to add it as a dependency

Added tag cubicweb-version-3.17.15, cubicweb-debian-version-3.17.15-1, cubicweb-centos-version-3.17.15-1 for changeset ee413076752b

[pkg] also bump __pkginfo__