XML-RPC: wp_upload_bits should act like wp_handle_upload

[markoheijnen]

At this moment there isn't a check for file size when uploading an image through the XML-RPC. The reason is that the method wp_upload_bits is used. This only checks it does is if the file size is to big for a network installation.

The function check_upload_size() is something what you want except that it will use wp_die() if there is an error like this. The function is used as a filter: wp_handle_upload_prefilter. Which only get applied in the function wp_handle_upload.

We should probably change check_upload_size() a bit so it doesn't use wp_die() but does it somewhere else.

related: #6559 and #21085

Related: #20057

Finding a way to add ​https://github.com/daniloercoli/WordPress-streaming-xml-rpc in the new media method. And when it works well in 3.5 also add it in 3.6 for the current one.

Just a weird thought. Would it make sense to fake a $_FILES array to pass through wp_handle_upload(). By using the code of Danilo to store the image localy that would make sense.

Other solution is not using it and fix wp_upload_bits(). Looking again to it and they should both do the same thing. The only difference is the input and how to act on that.

Uploaded my first try to fix the upload limit

Added unfiltered_upload capability check

Added a new patch that checks if a user can upload any file.