exp/nacl/av: update color to max out at 1<<16-1 instead of 1<<32-1. Fix missing return in Set(x, y, color).
exp/nacl/av: update color to max out at 1<<16-1 instead of 1<<32-1.
Fix missing return in Set(x, y, color).

R=r
CC=golang-dev
http://codereview.appspot.com/2256042

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