This patch adds basic support for ASSUME functions to VRP.

Based on the previous set of patches, Ive cleaned them up, and this 
provides the basic support from rangers generalized model. It does not 
support non-ssa name parameters, I think you might be on your own for that.

I modified Jakubs assumption pass to use GORI to query parameter rangers 
in assumption functions and set the global range for those, and then 
ranger's infer infrastructure is used to inject these rangers at assume 
call locations in VRP.

I also added an optimization testcase that tests the basic functionality 
in VRP2.  For instance it can reduce:

int
f2 (int x, int y, int z)
{
   [[assume (x+12 == 14 && y >= 0 && y + 10 < 13 && z + 4 >= 4 && z - 2 
< 18)]];
   unsigned q = x + y + z;
   if (q*2 > 46)
     return 0;
   return 1;
}

to:

return 1;


Its good to get us going, bt I think theres still lots of room for 
improvement.

Bootstraps on x86_64-pc-linux-gnu with no regressions.  Pushed.

Andrew