More advanced flag help support

[jokesper]

While looking at how other programs handle flags I found some special cases:

1. --[no-]xxxx, which is a pair of flags to override a boolean value, with one help and different resulting values.
   listing them both would also be ok (--xxxx, --no-xxxx)
   So this is a request of having one help for multiple options.
2. -Wxxx, which is often used to enable warnings in compilers,
   -W as a short flag is trivial, but we want to have multiple help pages per option with expanded valid values.

So I would like help pages not having to be in a 1:1 relation with options.