Edit some things, make sure all code runs.

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pointless/outdated idioms from the code.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.