The ABI changes should be completely transparent to Go code, but could
cause linking issues in certain situations involving assembly code
reaching across package boundaries. If users encounter linking
problems, point them to the "Compatibility" section of the ABI design
document, which gives some guidance.

Change-Id: I4156d164562e2ec0de7ae8f9a3631a32ec45b317
Reviewed-on: https://go-review.googlesource.com/c/158237Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>