Fix buffer stomping; retool Makefile.

The Makefile is now useful for building ke(1) to aid in more rapid
development. This works because ke doesn't (yet) need any special
non-system libraries.

File.h

@@ -80,12 +80,10 @@ public:
 	/// IsReadWriteable checks whether the current user has both
 	/// read and write permissions on the file.
 	bool			IsReadWriteable();
-
 private:
 
 	std::filesystem::path	path;
 	bool			readOnly;
-	std::ios::openmode	mode;
 };