compiler: Recognize 64-bit symbol tables in archives.
compiler: Recognize 64-bit symbol tables in archives.

By Dominik Vogt.

R=iant
CC=gofrontend-dev
https://golang.org/cl/154800044

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