697f1e38d6
This comes with a terminology change. All linkage-symbols are 'extern' now, including rust syms in other crates. Some extern ABIs are merely "foreign". The term "native" is retired, not clear/useful. What was "crust" is now "extern" applied to a _definition_. This is a bit of an overloading, but should be unambiguous: it means that the definition should be made available to some non-rust ABI.