Send is no longer a subkind of copy. This allows for sendable, but non-copyable resources. Closes #2420.

And remove support for the old syntax

This involved adding 'copy' to more generics than I hoped, but an
experiment with making it implicit showed that that way lies madness --
unless enforced, you will not remember to mark functions that don't
copy as not requiring copyable kind.

Issue #1177

Issue #1076

Closes #1067

XFAIL the ones that don't work

Issue #409