XML-RPC newMediaObject should try to work out mime-type if not supplied

[jonquark]

At least one XML-RPC client (MaStory on Maemo) does not set the type parameter on uploaded objects. This means we don't create appropriate thumbnails correctly.

Given some clients are on fairly low-power, simple devices, it's probably worth Wordpress attempting to determine the mime-type, especially as functions calls we /already/ make on attachments will give us that information already for the common-case of image uploads.

If not supplied, determine mime-type for uploaded images

I'd suggest running this through get_allowed_mime_types() before assuming that the upload is an image.

Alternative patch..now works with non-image mimetypes

Hi Joseph,

When I came to address your comment, I realised that there is a wp_check_filetype() that works with a broader range of mime types.

I've attached a version of the patch that uses it (and also stops passing type to wp_upload_bits as that is deprecated in favour of a call to wp_check_filetype()).

Does that seem reasonable?