Updating commentary about PrimOps and codegen

[Jan Stolarek]

Hi all,

I've been reading Commentary about PrimOps and code generation and I noticed that it is partially 
outdated (e.g. references to old code gen files: compiler/codeGen/CgPrimOp.hs):

http://hackage.haskell.org/trac/ghc/wiki/Commentary/PrimOps
http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/CodeGen

Would anyone be so kind to update these pages and possibly other pages about code generation, STG, 
Cmm and related stuff? I've been trying to figure out how to add new PrimOps and having up to 
date documentation would be most helpful.

Janek