FMSLogo Code

Use wxFopen() instead of fopen().
This was done to help port FMSLogo to Unicode.

Merge in changes from trunk

Remove the "Null_Word != NIL" test in make_strnode_no_copy().
It's a bug if Null_Word is not initialized by the time make_strnode_no_copy is called, so it's sufficient to assert it.

Change the string header of NODE* from char* to unsigned short*
Although it's not obvious, this adds some type safety because the header was always treated as a reference count (unsigned short), not a char*.
This was done to help prepare the code for being ported to Unicode, as the size of the header won't change, even if the size of a character does.

Add some comments

Refactoring: restructure open_file to remove duplicated code.
Also add comments and reduce the scope of th WX_PURE block.

Add regression tests that SETREAD and CLOSE are case-sensitive for the reserved filename "clipboard", even though it can be opened with any case.

Add regression tests that SETREAD/SETWRITE/CLOSE must exactly match the file name.

Replace some RUNBADINPUTTEST with RUNDOESNTLIKEINPUTTEST.
RUNBADINPUTTEST is deprecated because it doesn't check the error code.

Add regression tests for reading from the clipboard with OPENREAD "clipboard