GetDiskFreeSpace("." | "..") fails on Win98 and NT4 but succeeds on XP
-> removed.
Skip the GetDiskFreeSpace tests on floppy drives because NT pops up a
MessageBox if no floppy is present.
Fix the error code checks to take into account the differences between
Win9x, NT4 and XP.
Skip the unicode tests if the first call returns
ERROR_CALL_NOT_IMPLEMENTED.
Whenever a test fails, print sufficient information (typically return
code and GetLastError()!) to let the developer figure out what is
wrong.