[dev.cc] liblink: fix Solaris build some more

a->name and a->class are char, so Solaris doesn't like using
them as array indexes.  (This same problem was fixed for amd64
in CL 169630043.)

LGTM=aram, minux
R=rsc, minux, aram
CC=golang-codereviews
https://codereview.appspot.com/175430043