[patch] Split DataLayout and DataLayoutPass

[Rafael Espíndola]

In order to use DataLayout from IRObjectFile it would be nice for it
to not be a pass and just be information associated with a module.

It seems to also be in the direction we want to go for make datalayout
mandatory.

What the attached patch does is split DataLayout and DataLayoutPass. I
am working on removing DataLayoutPass completely, but that involves
passing a DataLayout object to many places that only take a Value or a
Type and therefore cannot reach a Module.

Sending these for review first so the review can happen in parallel.

Cheers,
Rafael