cleanfile: a script to clean up stealth whitespace

This script cleans up various classes of stealth whitespace.  In
particular, it cleans up:

- Whitespace (spaces or tabs)before newline;
- DOS line endings (CR before LF);
- Space before tab (spaces are deleted or converted to tabs);
- Empty lines at end of file.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>