make rustdocs more terse for bool.rs where it is obvious to programmers as per feedback from graydon

Closes #1200

Closes #1326

This reverts commit c00ec5f9.

Closes #1489

By simply not resolving that def id until the typeck pass.

Closes #1494

Use ifaces instead of objs, stop wrapping everything in two (or three)
layers of no-value-added indirection, and remove some of the more
pointless/outdated idioms from the code.

We can now run the compiler with an iface-based hashtable
implementation.

This prevents trans_args from optimizing out nil return types. The
method might be generic, in which case it *will* write to a nil retptr.

Addresses issue #1393.

For now disallow disr. values unless all variants use nullary
contractors (i.e. "enum-like").

Disr. values are now encoded in the crate metadata, but only when it
will differ from the inferred value based on the order.

Something about the way we're using it is causing incorrect code generation.

Closes #1343

Also update the naturaldocs keywords file.

Closes #1396