README.md: move Windows instructions to separate file

Merge pull request #139 from oxpa/master

Three minor fixes

Check basic auth result against != NGX_OK rather than == NGX_DECLINED

This corrects the error handling case when ngx_http_auth_spnego_basic is called with a bad configuration or bad username. These cases return NGX_ERROR, which allowed basic auth to proceed.

Thanks to Prakapovich Pavel aka Flyguy.by for pointing this out.

Indentation and compile fixups after last merged pull requests

Closes #52

Update ChangeLog and README