Only the first constant in the function and facility
constant declaration blocks were typed constants.
Make all other constants used for function codes and
named facilities also typed.

Change-Id: I1814121de3733094da699c78b7311f99ba4772e1
Reviewed-on: https://go-review.googlesource.com/126776
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>