compiler: Always re-lower lowered expressions.
compiler: Always re-lower lowered expressions.

R=iant
CC=gofrontend-dev
https://golang.org/cl/5570063

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