Added SDL_round(), contributed by Benoit Pierre - thanks!

src/stdlib/SDL_stdlib.c

@@ -169,6 +169,16 @@ SDL_pow(double x, double y)
 #endif /* HAVE_POW */
 }
 
+double
+SDL_round(double x)
+{
+#if defined(HAVE_ROUND)
+    return round(x);
+#else
+    return SDL_uclibc_round(x);
+#endif /* HAVE_ROUND */
+}
+
 double
 SDL_scalbn(double x, int n)
 {