AP_Math: added fill_nanf()

used in SITL to invalidate memory

libraries/AP_Math/AP_Math.cpp

@@ -303,3 +303,11 @@ bool rotation_equal(enum Rotation r1, enum Rotation r2)
     return (v1 - v2).length() < 0.001;
 }
 
+
+// fill an array of float with NaN, used to invalidate memory in SITL
+void fill_nanf(float *f, uint16_t count)
+{
+    while (count--) {
+        *f++ = nanf("fill");
+    }
+}

libraries/AP_Math/AP_Math.h

@@ -281,3 +281,6 @@ bool is_valid_octal(uint16_t octal) WARN_IF_UNUSED;
 
 // return true if two rotations are equal
 bool rotation_equal(enum Rotation r1, enum Rotation r2) WARN_IF_UNUSED;
+
+// fill an array of float with NaN, used to invalidate memory in SITL
+void fill_nanf(float *f, uint16_t count);