Fix fucntion that return struct as values

[lassade]

follows these instructions: microsoft/win32metadata#636 (comment) to fix marlersoft/zigwin32#6

requires: marlersoft/win32jsongen#8

[marler8997]

Thanks for the contribution. Unfortunately these types of "zig update" changes are something I like to do myself so I can see what's changed between zig versions so I wasn't able to leverage your work. But the project now works with zig version 0.12.0-dev.2701+d18f52197 and the bindings themselves still work on 0.11.0 if you want to keep hacking.