[PATCH][4.5] Move gimplifier predicates

[Andrew Haley]

Richard Guenther wrote:
> This moves gimplifier predicates to where they belong and makes them
> private.  Apart from the uses in walk_gimple_op for which I have no
> clue what this monster-function tries to do - Diego, do you remember?
> 
> The java use seems unnecessary (as the comment hints).

I wrote that comment, and to my eyes it hints no such thing.

As the comment says, it was intended to make well-defined an expression
such as

   a + ( a = 2; )

by transforming it into

   ({ A = a; A + ( a = 2 ) })

Andrew.