Investigate windows-rs/windows-sys changes for 9x/Me/unicows support

[seritools]

• The default "god import" library is imported before unicows.lib, so it prevents unicows from working correctly
• target checks are too strict and wont link the god import library on rust9x anyways
  • this affects all additional targets like the new win7 one, so I created a fix PR for the official repo
• Switching to raw-dylib runs into Investigate raw-dylib support/workarounds for unicows #15.
• link! specifies library names with .dll, making it tricky to change it to #[link(name = "<libraryname>")]
  • one way would be to link everything, without raw-dylib, to kernel32, since kernel32 is always linked. Other dependencies will need to be manually specified in the link args, then.

[seritools]

I've added two branches to rust9x/windows-rs, one for NT-based Windows only and another one with 9x/Me/unicows support: https://github.com/rust9x/windows-rs/branches

Added info about it in the Limitation wiki entry as well.

[seritools]

All official releases that include microsoft/windows-rs#2774 should also work for NT-based systems.