Name collision on Windows

[GadgetSteve]

Performing a checkout on MS-Windows a warning is given:

warning: the following paths have collided (e.g. case-sensitive paths
on a case-insensitive filesystem) and only one from the same
colliding group is in the working tree:

  'upstream_doc/dox/LICENSE.md'
  'upstream_doc/dox/license.md'

It looks like the 2 files may be identical so suggest deletion of upstream_doc/dox/license.md to resolve this warning.