cgo: In _cgo_main.c define all provided symbols as functions.
cgo: In _cgo_main.c define all provided symbols as functions.

This defines crosscall2 in a way that matches that real
definition, and also defines _cgo_allocate and _cgo_panic to
indicate that they are available to be called by code compiled
with gcc.

R=rsc
CC=golang-dev
http://codereview.appspot.com/4026041

npe9/noahevans-go9,scirelli/scirelli-go,Triskite/willstone-goclone,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,d0f/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,scirelli/scirelli-go,d0f/go-zh,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,npe9/noahevans-go9,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,mhennings/marcohennings-go,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,npe9/noahevans-go9,Triskite/willstone-goclone,Triskite/willstone-goclone,sanjosh/sanjos100-tipc,webfd/go-zh,Triskite/willstone-goclone,sanjosh/sanjos100-tipc,webfd/go-zh,Triskite/willstone-goclone,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,bryanxu/go-zh,mhennings/marcohennings-go,bryanxu/go-zh,d0f/go-zh,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,npe9/noahevans-go9,rdp/rogerpack2005-golang,d0f/go-zh,webfd/go-zh,bryanxu/go-zh,rdp/rogerpack2005-golang,mhennings/marcohennings-go,mhennings/marcohennings-go,d0f/go-zh,rdp/rogerpack2005-golang,bryanxu/go-zh,npe9/noahevans-go9,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,webfd/go-zh,bryanxu/go-zh,mhennings/marcohennings-go,bryanxu/go-zh,bryanxu/go-zh,npe9/noahevans-go9,d0f/go-zh,npe9/noahevans-go9,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,npe9/noahevans-go9,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,scirelli/scirelli-go,mhennings/marcohennings-go,d0f/go-zh,sanjosh/sanjos100-tipc,Triskite/willstone-goclone,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,webfd/go-zh,rdp/rogerpack2005-golang,Triskite/willstone-goclone,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1