[Development] 64-bit QFlags support

[Kevin Kofler]

Thiago Macieira wrote:
> All of KDE libraries and applications, for example, don't care about MSVC
> compatibility

Huh, since when?

Last I checked, there were people building KDE Frameworks and several KDE 
Applications with MSVC (as well as with MinGW, but there are a few reasons 
why they do not support only MinGW for Windows builds, one of which being 
that QtWebEngine does not build with MinGW). Those people will definitely 
care about enum values not getting silently truncated in their builds.

        Kevin Kofler