Investigate and fix KILL command behavior

[mkilgore]

In #19 Steve was having troubles getting KILL to work with files that had spaces in the name. Based on the description of KILL here it seems like it should work if file names have spaces, but the C++ implementation sub_kill() looks fairly questionable and should be reviewed.

At the very least there is a clear difference between the Linux and Windows implementations because Windows uses FindFirstFile() which supposedly handles the * and ? wildcards, but Linux just uses remove() which does not. Additionally, there is a lot of weird/suspicious path handling in Windows that might have been what was giving Steve some trouble. Certainly DeleteFile() itself can handle spaces in paths.

IMO it would probably be worth just implementing the * and ? handling ourselves and use the same implementation for all platforms. That should hopefully also allow us to toss some of the weirder handling and get consistent behavior. We should also presumably verify the behavior of QuickBasic 4.5 a bit