Use std::sqrt

(cherry picked from commit 9c197e82a3b6742a7d2b521efe9cd9232e9ab8f1)

src/tools/vmap4_extractor/vec3d.h

@@ -103,7 +103,7 @@ public:
 
     float length() const
     {
-        return sqrt(x*x+y*y+z*z);
+        return std::sqrt(x*x+y*y+z*z);
     }
 
     Vec3D& normalize()
@@ -209,7 +209,7 @@ public:
 
     float length() const
     {
-        return sqrt(x*x+y*y);
+        return std::sqrt(x*x+y*y);
     }
 
     Vec2D& normalize()