Each numeric type now contains an extensions module that is automatically
exported. At the moment each extensions module contains only the impl for the
`num::num` iface. Other impls soon to follow (hopefully).

and mention *-patterns and the removal of resources

This was already fixed by the time I read the issue, but more test
cases are always good.

Closes #2718

This tests == and !=. I don't know what <, >, etc. should do.
Closes #2601

Tests that classes with dtors and multiple fields work correctly.
Closes #2708

Also fixed shapes for classes with dtors, as well as handling
offsets for classes with dtors correctly in take glue.

Closes #2485

I hereby declare that messages sent from the same source arrive in order (Issue #2605)

Removing FIXME, owned is the correct type here. (Issue #2704)

Remove outdated FIXME (Issue #2703)

Updating test for spawning native functions (Issue #2602)

Removing bogus FIXME (Issue #2599)

Make the implicit copyability of []/~ configurable, like [] is, since we will be switching sooner rather than later.

since dtors always have external linkage