Fix intermittent crash with older MinGW releases

An alternate code-path was previously added to work around a bad
signature for the SHParseDisplayName() function in older and non-w64
versions of the MinGW headers. This code-path incorrectly passed a
single rather double indirect pointer to the third argument of that
function causing it to produce corrupt data and subsequently crash.
This change modifies the code to instead cast a pointer of the correct
type to the incorrect type expected by the headers.

Task-number: QTBUG-39793
Change-Id: I4d65dea4fc38d7e885468cd23434d8570c311fc2
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>