attaching "image as files" still recodes the file

[r10s]

attaching "image as files" still recodes the file.

this is a new bug in one of the current cores, for 1.44 it is fine. the bug is in all recent UIs on current "master", that have been fine before, so it is pretty likely a core bug

maybe introduced by the fixes wrt GIF encoding, cc @iequidoo

as we're recoding also PNG to JPG, these is no way left to send a file uncompressed, i think, this needs to be fixed before the 1.46 release

as there are often degradations in that area, i think, we also need more test here