go.tools/go/loader: fix Solaris build
go.tools/go/loader: fix Solaris build

Also fix one test that failed on Plan 9.

LGTM=0intro, dave
R=golang-codereviews, 0intro, dave
CC=golang-codereviews
https://codereview.appspot.com/101370053

Committer: Dave Cheney <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@cheney.net>

karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools