Changed the check for the radius being zero a little more robust against

floating point weirdness.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403983

dlib/optimization/optimization_trust_region.h

@@ -282,7 +282,7 @@ namespace dlib
 
                 // something has gone horribly wrong if the radius has shrunk to zero.  So just
                 // give up if that happens.
-                if (static_cast<type>(radius) == 0)
+                if (static_cast<type>(radius) <= std::numeric_limits<type>::min())
                     break;
             }
             else