Make the interface to the transport peers functions more formal:
define when each function is called and what (roughly) it should do.
Remove the predeclaration of transport_record_peer. This is now an
internal function for the transport peer management code; there are no
callers in the body of site.c and we can remove the declaration.
No functional change.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>