cmd/cgo: support Linux/ARM         Part 3 of CL 5601044 (cgo: Linux/ARM support)
cmd/cgo: support Linux/ARM
        Part 3 of CL 5601044 (cgo: Linux/ARM support)

R=golang-dev, dave, rsc
CC=golang-dev
http://codereview.appspot.com/5991066

glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,bryanxu/go-zh,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,scirelli/scirelli-go,d0f/go-zh,mhennings/marcohennings-go,Triskite/willstone-goclone,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,scirelli/scirelli-go,bryanxu/go-zh,mhennings/marcohennings-go,rdp/rogerpack2005-golang,webfd/go-zh,sanjosh/sanjos100-tipc,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,Triskite/willstone-goclone,webfd/go-zh,rdp/rogerpack2005-golang,webfd/go-zh,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,d0f/go-zh,rdp/rogerpack2005-golang,d0f/go-zh,scirelli/scirelli-go,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,d0f/go-zh,d0f/go-zh,d0f/go-zh,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,Triskite/willstone-goclone,d0f/go-zh,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,bryanxu/go-zh,mhennings/marcohennings-go,webfd/go-zh,Triskite/willstone-goclone,webfd/go-zh,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,scirelli/scirelli-go,Triskite/willstone-goclone,Triskite/willstone-goclone,bryanxu/go-zh,scirelli/scirelli-go,sanjosh/sanjos100-tipc,Triskite/willstone-goclone,webfd/go-zh,mhennings/marcohennings-go,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go