FMSLogo Code

Fix bug #484; BYE now immediately exits when run at the top-level of a file that is loaded from the command-line.

The heart of the fix is to make all primitives return an Unbound value when exiting to avoid the "you don't say what to do with" errors. The rest of the changes udpate all parts that of the code that evaluate Logo code to do so within a start_execution() and stop_execution() so that a "close" event can be sent if the application is exiting.

Simplify the shutdown logic. Also fix a bug that caused the debug screensaver to have assert failure (the size of the wxTempDC needed to be set)

Correct the names of global variables and a function in a comment (this was a copy&paste legacy from the OWL implementation).

Fix a copy&paste error that prevented the second line of CSaveBeforeExitDialog from being wrapped. This didn't matter in practice because the second line is shorter than the wrap-size (at least in English)

Add some comments to CWorkspaceEditor::OnClose() which explain why code calls endedit() twice.

Fix a regression that was introduced by moving the delayed Close() call from the idle event to stop_execution() that made FMSLogo think that the workspace was dirty if you halted a program during its "startup" execution. Since it's common for a program to never return from its "startup", this regression made it so that FMSLogo would give a strange warning when any program was running.

The fix was to restore the "IsDirty" flag in-between when a file is loaded and when its "startup" list is run, instead of after the startup list is run.

Implement feature #33; Make it so that FMSLogo doesn't mind exiting while running and remove the "Logo doesn't like to exit while running" dialogs.

This involved moving the delayed Close() invocation from the idle loop to the point where the evaluation engine has fully unwound. Then some logic was added to the OnClose() to halt the language engine if it is running.

Integrate a regression test for bug #484 into the full test pass.

Simplify the exit path by removing prepare_to_exit(), which was legacy from UCBLogo that didn't make sense in FMSLogo and only obscured the shutdown mechanics.

Add a regression test that actually runs BYE (by running it in a child instance)