Add comments re. max message length (https://github.com/tbuktu/libntru/issues/11)
Add comments re. max message length (https://github.com/tbuktu/libntru/issues/11)

jl777/libntru,iblumenfeld/libntru,jl777/libntru,jquesnelle/libntru,iblumenfeld/libntru,jquesnelle/libntru,iblumenfeld/libntru,jl777/libntru,jquesnelle/libntru