Documentation for loop infrastructure

[Daniel Berlin]

Zdenek Dvorak wrote:
> Hello,
> 
> this patch adds documentation for loop analysis and representation of
> loops, as well as other loop-related analyses, and for functions to
> manipulate loops.  As I am not a native English speaker, there are
> probably many language errors in the document, so I would appreciate
> if someone could read it and fix them.
> 
> Also, the sections regarding data dependence analysis and lambda
> framework are missing.  Sebastian, Daniel, do you have time to write
> them? 

I can write up something on lambda.