rustdoc: Remove definitions of spawn_listener and spawn_conversation
rustdoc: Fix some search-and-replace fallout
rustdoc: Remove another use of oldcomm
rustdoc: Remove stray mode
rustdoc: Convert to pipes
core: Remove oldcomm
rt: Remove ports
rt: Remove circular_buffer
rt: Remove get_frame_glue_fns. Unused
rt: Remove some unused upcalls