Fix speedkeys to move subtrees up and down
* lisp/org.el (org-speed-commands-default): Bind "U" and "D" to
`org-metaup' and `org-metadown'.
Org speed keys were not updated to reflect the recent changes to
org-shiftmetaup and org-shiftmetadown. As a result the default
bindings for speedkeys "U" and "D" were destructive, since they moved
only single lines. Binding them to org-metaup and org-metadown fixes
Thanks to Marco Wahl for reporting the problem: