Fix a problem with Function_declaration::import_function relating to
    how no-name or "sink" parameters are handled. In Gogo::start_function
    (for the non-inline case) when parameter bindings are being added,
    parameters with empty/sink names are renamed to synthesized "r.%d" /
    "p.%d" names so as to avoid collisions. This same handling needs to be
    present when creating the bindings for an inline function that's being
    instantiated after being read from export data.
    
    Fixes golang/go#31637.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/173538

From-SVN: r270564