make sure $meta->{'meta-spec'}{version} returns a valid version

- as it dies abruptly when $meta->{'meta-spec'} illegally returns a
  scalar spec version (example: JOSEPHW/XML-Writer-0.600.tar.gz)
Improved fix for scalar meta-spec field

If 'meta-spec' is not a hash reference, this now treats it like a 1.0
spec (when 'meta-spec' was not defined).  It will convert 'meta-spec' to
a valid hash reference during conversion.  This allows possibly
'rescuing' a bad META file.

It also adds t/README-data.txt to clarify where to put data files (since
I'd forgotten myself and had to figure out what we meant with each
directory).
Cope with weird/invalid meta-spec version keys

Checks for bad spec versions and fixes with some heuristics.
further reorganize test data
ASCII-fy Dolmen Mengué in mailmap to keep spell check from crashing
relax check for existing 'generated-by' signature
update Changes