Add support for attaching 32-bit binaries on amd64.
Add support for attaching 32-bit binaries on amd64.

nelhage/reptyr,nelhage/reptyr,developerfm/reptyr,jerome-pouiller/reredirect,nelhage/reptyr,developerfm/reptyr,yatsek/reptyr,developerfm/reptyr,jerome-pouiller/reredirect,yatsek/reptyr,yatsek/reptyr