Don't store error types in the Type-to-GENERIC hash table.
Don't store error types in the Type-to-GENERIC hash table.

R=iant
CC=gofrontend-dev
https://golang.org/cl/3656041

qskycolor/gofrontend,golang/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,golang/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,golang/gofrontend,golang/gofrontend,anlhord/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,anlhord/gofrontend,anlhord/gofrontend