FMSLogo Code

Update the tests so that a full test pass can run on GNU/Linux.
In some cases, this meant finding ways to make tests run differently on Windows or GNU/Linux.
In most cases, this meant not running tests whose execution depends on Windows,
such as any test that uses UIAUTOMATIONLIB, which uses DLLCALL for win32 API.

Refactoring: Replace CURRENTWORKINGDIRECTORY with GETCURRENTDIRECTORY in dllcall.
This removes duplicated code.

Adjust some of the assert statements that I had added to the inline functions.
The getstr* functions now call is_word() which works for all string types.
Confusingly, is_string() is a special case of is_word().

Also treepair__tree is not always called on a tree.
This may be a bug, which I'll look into later.
For now, it's more important for fmslogo to run with asserts than to have this assert.

Fix a typo in a comment

Comment out the "assert(is_tree(tree))" that I recently added to settreepair__tree(tree, treepair).
There are code paths, notably in treeify_line, which invoke untreeify on nodes that aren't trees.
That could be a bug, but having the assert is counter-productive as it currently fires on nearly any procedure call.
If the untreeify logic can be rewritten to only be invoked on trees, then I will re-enable the assert.

Add comments to explain the purpose and function of the two different stacks used by the evaluator.

Fix an inaccurate claim in a comment.
MSWLogo did not sort the output of FILES and DIRECTORIES.
That was a fix made in FMSLogo 6.33.0.

Rewrite directory_helper in terms wxWidgets instead of in terms of WIN32 API.
This makes FILES and DIRECTORIES work on GNU/Linux.

Replace "TRUE" with "true" because ther literal is used as a bool, not a BOOLEAN.

Change some #define constants into "const" values.
This makes the symbols available to the debugger, which can help with debugging.