Windows APIs don't really provide a way to change a filename case. This
implements a little juggling to make this work. We first create a
guaranteed unique temporary file, we then replace the original file with
the temporary file and we finally rename it to the desired filename
case.
(cherry picked from commit d69d58deeaa523c6c38958b3956423ae8f814909)
Hein-Pieter van Braam
8cde69f5f2