
* MacOS: bitmaps don't print (with MacOS-specific printing)

* Windows and MacOS: "primitive" dialogs don't get closed by
  custodian-shutdown-all

* MacOS: std file dialog and print dialogs block MzScheme threads

* Unix: Clipboard client is invoked in the wrong thread/eventspace

* Need to penalize the current thread more (i.e., swap it out sooner)
  after certain primitive operations that can take a long time (e.g.,
  loading a bitmap or saving a file)

* Windows: System menu navigation in a menuless MDI window leads to a
  crash

* A top-level-window<%>'s on-move method is not reliably called; also,
  the result from get-x, get-y, and is-iconized? are not reliable
