Migrate TODO.md to issues...

[rrnewton]

These should go into github issues

TODO

• Add a TupleSize variant to ArraySizeEstimate to deal with Scanl'.
  (Or just get rid of Scanl/r'!!)
• FreeVars should somehow be attached to specific Lambdas, not to
  array ops.
• types like Type, Prim, Const should probably be reexported by GPUIR
  and CLike IRs so that those modules are self contained.
• GPUIR needs an overhaul. Kernel declaration probably need to be
  separate from kernel invocation (e.g. a fold will be multiple
  kernel launches), and kernels need to have local work size as well
  as global.
• The interpreters are in disarray. It would be nice to have a fully
  functional interpreter for all three major IRs.
• UnzipETups: really needs to use maybeLet
• (BUG) p20* was exposing a bug where a singleton ETuple would appear
  out of OneDimensionalize.
• FuseGenReduce: inline Cond's as well.
• InlineCheap should inline Use dereferences.
• Perhaps factor TArray into its own type. It really shouldn't be
  mixed up with the scalar types, this just encourages incomplete
  pattern matches.
• Why don't we use Word instead of Int by default for all shape
  related stuff?
• Fix sizeAnalysis to work for the replicates in Nbody. Is it not
  seeing through "EShape"?
• Compile EIndexScalar of known index into Use by just doing the
  dereference...

DONE

• Need to track the FULL SHAPE of any progResults for reconstructing
  the final thing. (Fix OneDimensionalize & downstream)
  -- ?? Is this still relevant? [2013.03.03]
  -- No, WithShapes should address [2014.02.24]