First big patch to fix -Wunused-local-typedefs

-Wunused-local-typedefs is a new warning flag of gcc-4.7, and it will enabled
 by -Wall since gcc-4.8 (not yet released).

The fix is a big set of removals of unused typedefs (or comments, or moves,
depending on the context).

Homogeneous_kernel/include/CGAL/Homogeneous/function_objects.h

@@ -739,7 +739,6 @@ namespace HomogeneousKernelFunctors {
     result_type
     operator()(const Line_2& l1, const Line_2& l2) const
     {
-      typedef typename K::RT RT;
       if (l1.is_horizontal())
 	return l2.is_vertical() ?
 	  SMALLER : CGAL_NTS sign(l2.a()) * CGAL_NTS sign(l2.b());
@@ -1047,7 +1046,6 @@ namespace HomogeneousKernelFunctors {
     result_type
     operator()( const Point_2& p, const Line_2& h) const
     {
-      typedef typename K::RT RT;
       CGAL_kernel_precondition( ! h.is_vertical() );
       typename K::Oriented_side ors = h.oriented_side( p );
       if ( h.b() < 0 )