Ensure GeomLib::NormEstim won't last for ever

This patch make the following program run in 0.01s instead of 80s. The created mesh have 132 triangles.

```
#include <BRepTools.hxx>
#include <iostream>
#include <BRep_Builder.hxx>
#include <BRepMesh_IncrementalMesh.hxx>
#include <BRep_Tool.hxx>
#include <Poly_Triangulation.hxx>
using namespace std;

int main()
{
    BRep_Builder bb;
    TopoDS_Face shape;
    TopLoc_Location loc;
    cout << BRepTools::Read(shape, "slowmesh.brep", bb) << endl;
    BRepTools::Clean(shape);
    BRepMesh_IncrementalMesh(shape, 5, false);
    const Handle(Poly_Triangulation) triangulation = BRep_Tool::Triangulation(shape, loc);
    cout << triangulation->NbTriangles() << endl;
    return 0;
}
```

The slowmesh.brep file. https://gist.github.com/9af35df566db197856c1