Document MSVC doesn't straddle bit-fields

[workingjubilee]

This PR documents existing behavior in the MSVC toolset.

[PRMerger15]

@workingjubilee : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[ktoliver]

#label:"aq-pr-triaged"

[PRMerger13]

@corob-msft : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[colin-home]

@workingjubilee
Thanks for the contribution. We mention this implementation-specific behavior in a very oblique way in Padding and alignment of structure members, and in the Bitfields section of x64 software conventions (though the compiler behavior isn't x64-specific). Those pages aren't necessarily where people would go to find this out, so this seems a good place to add that info. I've modified your content to follow our voice and internationalization guidelines.

[workingjubilee]

Ah, I missed that. Thank you, cross-referencing it does seem appropriate.