In the iPhone version, add functions to query Location Services (GPS),
accelerometer, and compass. This functionality should be optional, for perfect
42S compatibility.

All versions: implement the Time Module functions, as far as possible.
This functionality should be optional, for perfect 42S compatibility.

PalmOS: Flag 11 doesn't work on power cycle: After exit and restart, it does
work; after power cycle, the "running" annunciator comes on, but the program
does not actually run. Sounds like the event queue needs to be prodded.

The whole flag 11 thing seems flaky on several platforms.
Also, what about  LBL "NASTY"  SF 11  OFF  GTO "NASTY"  ?
I think we should have some kind of check for the case where the calc does OFF
without ever having handled any kind of user events since power-on; it should
either refuse to power off, or clear flag 11 before powering off, or do some
kind of user interaction to give the user a chance to break this potentially
inescapable cycle.

Add keyboard click option for the Pocket PC version.

Add a feature for importing and exporting variables from and to CSV files.

The "print" annunciator should be more noticeable -- make it linger a bit.

PalmOS version: turning off spooling to GIF appears not to flush the file, so
you end up with a truncated GIF file.

Make '\' act as R/S even in ALPHA mode. R/S is important, and the backslash is
not, in the HP-42S part of the universe, anyway.

PalmOS version: add explanation to README.txt about skins -- why they won't
work off an SD card, how to install them properly, yada yada yada.

SOLVE: detect more sign reversals (not just the ones where the sign reversal
brackets a domain error). This isn't strictly a bug, since it is mathematically
impossible to reliably tell poles from zeroes (the real HP-42S doesn't always
get it right either), but there is clearly some room for improvement.