better readability..

src/stdlib/SDL_string.c

@@ -549,7 +549,7 @@ SDL_utf8strlen(const char *str)
     const char *p = str;
     char ch;
 
-    while ((ch = *(p++))) {
+    while ((ch = *(p++)) != 0) {
         /* if top two bits are 1 and 0, it's a continuation byte. */
         if ((ch & 0xc0) != 0x80) {
             retval++;