The new tool (mkconstfs2) features:
* more robust filename handling: no need for mangling,
and works on Windows.
* Better output generation: nothing is written in case
of failures.
* Allows more control over the files that are included:
- does not traverse directories, filenames must be explicitly
given.
- The "root" can be explicitly given (thus the tool can get
the same result independently of the CWD).
Thanks to MichelRottleuthner for making it work with Windows paths.
