A miscellaneous use of boost.

Sinc(x) is a simple function used in communications. boost
happens to use it for quaternion math. The implementation is
simple, however it looks fun to re-use the boost function
even if just to say we are using quaternion math somewhere ;).

The performance difference is not likely to be huge but JIC,
set up a specific Boost math policy to limit type promotion
with it's corresponding impact.
(cherry picked from commit d1f61b3f)

Conflicts:
	vcl/inc/vcl/bitmap.hxx

Change-Id: I5f01db1688eedee25a2943ca3aa6e957b400c759

include/vcl/bitmap.hxx

@@ -20,6 +20,7 @@
 #ifndef _SV_BITMAP_HXX
 #define _SV_BITMAP_HXX
 
+#include <boost/math/special_functions/sinc.hpp>
 #include <tools/color.hxx>
 #include <tools/link.hxx>
 #include <tools/solar.h>
@@ -207,7 +208,8 @@ public:
 
 class Lanczos3Kernel : public Kernel
 {
-
+    typedef boost::math::policies::policy<
+        boost::math::policies::promote_double<false> > SincPolicy;
 public:
     Lanczos3Kernel() : Kernel () {}
     virtual double GetWidth() const { return 3.0; }
@@ -223,7 +225,7 @@ public:
             return 1.0;
         }
         x = x * M_PI;
-        return sin(x) / x;
+        return boost::math::sinc_pi(x, SincPolicy());
     }
 };