Fixed a bunch of compiler warnings.

src/stdlib/SDL_qsort.c

@@ -362,7 +362,7 @@ typedef struct { char * first; char * last; } stack_entry;
 
 static char * pivot_big(char *first, char *mid, char *last, size_t size,
                         int compare(const void *, const void *)) {
-  int d=(((last-first)/size)>>3)*size;
+  size_t d=(((last-first)/size)>>3)*size;
 #ifdef DEBUG_QSORT
 fprintf(stderr, "pivot_big: first=%p last=%p size=%lu n=%lu\n", first, (unsigned long)last, size, (unsigned long)((last-first+1)/size));
 #endif