cmd/gc: run escape analysis in call graph dependency order
cmd/gc: run escape analysis in call graph dependency order

If there are mutually recursive functions, there is a cycle in
the dependency graph, so the order is actually dependency order
among the strongly connected components: mutually recursive
functions get put into the same batch and analyzed together.
(Until now the entire package was put in one batch.)

The non-recursive case (single function, maybe with some
closures inside) will be able to be more precise about inputs
that escape only back to outputs, but that is not implemented yet.

R=ken2
CC=golang-dev, lvd
http://codereview.appspot.com/6304050

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