Fix MyMemSet

The call to SetMem had n and c parameters reversed so that n was usually zero so nothing got cleared.

Author: joevt

libeg/lodepng_xtra.c

@@ -105,7 +105,7 @@ int MyStrlen(const char *InString) {
 } // int MyStrlen()
 
 VOID *MyMemSet(VOID *s, int c, size_t n) {
-    SetMem(s, c, n);
+    SetMem(s, n, c);
     return s;
 }