Remove undocumented page?

[ehuss]

I feel like the undocumented page is not particularly useful. It is very incomplete, and not kept up-to-date. I'd like to propose removing it, and just adding a link to the issue tracker in the introduction. Taking a close look at the current items:

• libstd facade — Looks like this RFC never hit its potential, I consider it not relevant.
• Trait reform – Somewhat documented (coherence, orphan rules, method resolution order, Self types are all at least partially covered).
• Flexible target specification — I believe conditional compilation is now complete (except target_feature).
• dllimport — I have expanded slightly docs on link, but it could explain more.
• define crt_link — Don't think this is relevant.
• impl Trait — Tracked in Document impl trait (RFC #1522, RFC #1951, RFC #2250) #276.

Agree/disagree?