FMSLogo Code

Add clearer documentation about how \n is handled (including within vertical bars)

Change the string node header from unsigned short to wchar_t.
This fixes an alignment problem on GNU/Linux, where wchar_t is four bytes, but short is 2 bytes.
It also makes the code look cleaner by removing a lot of type casting.
This should have no effect on Windows, where wchar_t and short are both 2 bytes.

Refactoring: Rework the string printing logic to use pointers instead of array indices
This makes the code smaller to offset the recent changes in to print "\n"

Refactoring: Change parameter type of is_vbarred/vbar_set/vbar_clear from int to wchar_t.
This adds a little bit of type safety.

Fix a bug that made the editor not show the "to/end" template when it was opened.
This was a regression from 7.7.0 introduced by the Unicode support. And an empty workspace is now written as a UTF-8 BOM instead of an empty file, so testing for a zero-sized file is no longer a valid way to determine if there is nothing in the file.

Fix a shutdown crash when the screen was occulded and the workspace was dirty.
In this case a screen re-paint message could come in after the main frame had been closed.
The fix is to simply ignore the re-paint message in this case.

This was a regression from FMSlogo 7.7.0. I don't know what caused it, but it might be that updating wxWidgets changed something subtle in the way it handles messages.

Fix a typo in a comment.

Fix Bug #551; Esscaped newline characters now SAVE as "\n"
Before, it saved as a backslash followed by a literal newline character.
This provides symmetry with the the logic that George Mills added to the tokenizer which converts "\n" into a newline and results in a nicer-looking workspace when saved.

Update with the results from another test pass of FMSLogo 8.0.0pre

Fix a typo in a file name that blocked the full test pass from running.