[Bug 45320] cmd creates an environment variable with an empty name

https://bugs.winehq.org/show_bug.cgi?id=45320

--- Comment #15 from Dima Ryazanov  ---
The doc is above msvcrt_SnapshotOfEnvironmentA, line 65.

I didn't even think about the memcpy... I guess technically, copying all of
environ_strings would be incorrect, too, but it does seem like a very minor
problem.

I'll try this on Windows, and see if environ/wenviron actually follow that
format exactly.