FMSLogo Code

Merge some typo fixes from trunk.

Fix a misleading comment.

Fix a typo in a comment.

Integrate latest changes from trunk into the unicode branch.

Remove CLEARPALETTE from DEMO.
CLEARPALETTE has been a deprecated no-op since FMSLogo 7.0.0.

Remove a #ifdef WXPURE by replaceing MessageBox with nearly equivalent wxMessageBox.
This is not exactly the same because the original used the deprecated MB_ICONQUESTION, which wxWidgets doesn't support.
This is a small step toward to a native GNU/Linux version of FMSLogo.

Add a regression test that SAVE displays a warning if run while the editor is open.

Replace some logic that copied a file with wxCopyFile.
This is clearer and probably faster and more correct.

Replace unlink with wxRemove.
This helps with porting FMSLogo to Unicode, as wxRemove works for both char* and wchar_t*.

Fix Bug #529; OPENREAD "clipboard no longer corrupts the line endings.