Also generate the constants using mkerrors.sh instead of having to list
each of them manually in types_solaris.go

In order to avoid _*_MAGIC constants being generated, also adjust the
corresponding rule in mkerrors.sh

Change-Id: If9193b12c2a2ec3b509a324be78329fee35a240d
Reviewed-on: https://go-review.googlesource.com/130355
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>