make sources compile again on MSVC 2012 (VC 11) by adding round()

modules/line_descriptor/src/binary_descriptor.cpp

@@ -41,6 +41,19 @@
 
 #include "precomp.hpp"
 
+#ifdef _MSC_VER
+    #if (__cplusplus <= 199711L)
+        /* This function rounds x to the nearest integer, but rounds halfway cases away from zero. */
+        static inline double round(double x)
+        {
+            if (x < 0.0)
+                return ceil(x - 0.5);
+            else
+                return floor(x + 0.5);
+        }
+    #endif
+#endif
+
 #define NUM_OF_BANDS 9
 #define Horizontal  255//if |dx|<|dy|;
 #define Vertical    0//if |dy|<=|dx|;