Make PseudoScreens resizable

[DaleStan]

For some value of "resizable", (some?) PseudoScreens should be resizable. This is a complicated problem involving both the window size and the content size, but it would be nice to allow #321 without reducing the width of the NEIE for all users. It would also be nice to let the Preferences screen increase in height beyond the maximum height allowed in a 60-unit-high window, when available.

This doesn't necessarily mean that and related mouse cursors must appear in appropriate places at appropriate times, just that the sizes should not be compile-time constants.