FMSLogo Code

Cleanup: Remove the need for assign.val

Cleanup: Remove redundant checks for NULL

Fix Bug #592; Complex usage of POLYSTART/POLYEND no longer causes FMSLogo to become unstable.
This was a regression in FMSLogo 7.0.0 by some cleanup in 3dsolid.cpp.
The fix is to redo the cleanup correctly.
It adds some code that shouldn't have been removed and removed some code that should have been.

This change was prepared by diffing the changes made in 7.0.0.
I don't have a good understanding of the code, nor do I really understand what these changes do.

Add a test for the interaction between dynamic scoping and ERASE.
ERASE can erase a dynamically scoped variable, but when it goes out of scope, so does the fact that it was erased.
This test was added as a regression test for Support Request #50 (a promise to maintain this behavior)

Add a little more tolerance for the duration test to account for the overhead of checking the time before and after the instruction.

Fix Bug #218; TONE/SOUND are now haltable.
Fix Bug #591; The sounds from TONE/SOUND now appear as coming from
FMSLogo in the Windows Volume Mixer instead of from System Sounds.

This was done by creating a waveform in memory and using wxSound to start
and stop it. While the sound is playing, the code checks the message queue
for new events (like a Halt).

Rewrite TIMECOMMAND to be more efficient and not to depend on LOCALMAKE

Add a test that TONE takes about :duration amount of time.
This is a close proxy for it playing the sound for :duration.

Remove the dependency on LOCALMAKE and make small stylistic changes.

Document what happens if you ERASE a variable that shadows another variable via dynamic scoping.
This is part of the resolution for Support Request #50.