debug/elf: handle Alpha relocs
debug/elf: handle Alpha relocs

Patch by Uros Bizjak.

Change-Id: I75635a22810f058301bbc4a7fbd1421ed6cc84e6
Reviewed-on: https://go-review.googlesource.com/46391
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

golang/gofrontend,golang/gofrontend,golang/gofrontend,golang/gofrontend