cmd/ld: cast PE32 absolute addend to int32. Didn't manage to find a way to write test cases.
cmd/ld: cast PE32 absolute addend to int32.
Didn't manage to find a way to write test cases.

Fixes issue 7769.

LGTM=iant
R=iant
CC=golang-codereviews
https://codereview.appspot.com/88000045

wesolows/golang,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old