The old binary/url is no longer available, and the layout of the
sourceforge archvie seems to have changed to include a new
old_versions/ directory where the previous binary is
relocated.
https://sourceforge.net/projects/winflexbison/files/old_versions/
While we could use that, it seem better to invest the effort to
adapt the scipt afterwards to use the github archives instead
https://github.com/lexxmark/winflexbison/releases
So for now bump the version to get the subproject building
till we switch to github releases.
This to simplify the checks made when for example a flex binary
is available system wide: the build process was failing when
that system wide binary didn't have the required version. Instead
of adding more checks and making things more complex, let's just
always use our binary subproject.
