FMSLogo Code

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.

Fix a bug in tone() where clicking "Halt" would halt the tone but cause the next command to throw a "Stopping..." error.
Now the TONE/SOUND commands throws the Stopping... error.

Fix a grammatical error

Replace the use of SOUND with TONE.
TONE is a little simpler, since it does require that the inputs be enclosed in a list.

Add a comment that explains why tone() sets frequency to 37 if it's below 37.