connect/bind export `*sockaddrin`, so under --sep the .wwi producer's
check_exported_type (both stages, correctly) rejects an exported decl
referencing the unexported type. Invisible on the old combined path
(net inlined, fed to w6c without -I). Hare exports sockaddr_in
(ref/hare/sys/+linux/socket.ha:11) and lib/net plays Hare's sys role,
so the caller must be able to name it. Same class as #48. No codegen
change (export is a checker property); byte-id holds.
Hojun-Cho
4583977ce0