Move the file (or directory) named FILENAME to the trash.
When `delete-by-moving-to-trash' is non-nil, this function is
called by `delete-file' and `delete-directory' instead of
deleting files outright.
If the function `system-move-file-to-trash' is defined, call it
with FILENAME as an argument.
Otherwise, if `trash-directory' is non-nil, move FILENAME to that
directory.
Otherwise, trash FILENAME using the freedesktop.org conventions,
like the GNOME, KDE and XFCE desktop environments. Emacs only
moves files to "home trash", ignoring per-volume trashcans.