[dev.link] all: merge branch 'master' into dev.link

Clean merge.

Change-Id: I6a39d0c00c7455ad0ce3dfe582a5f16d85857f51

diff --cc src/cmd/compile/internal/gc/iimport.go
Simple merge

diff --cc src/cmd/internal/obj/plist.go
Simple merge

diff --cc src/cmd/link/internal/ld/data.go
Simple merge

diff --cc src/cmd/link/internal/ppc64/asm.go
Simple merge