vlc_alloc: use multiplication overflow helper

Signed-off-by: Thomas Guillem <thomas@gllm.fr>

include/vlc_common.h

@@ -961,7 +961,7 @@ VLC_API bool vlc_ureduce( unsigned *, unsigned *, uint64_t, uint64_t, uint64_t )
 VLC_USED VLC_MALLOC
 static inline void *vlc_alloc(size_t count, size_t size)
 {
-    return likely(count * size >= size) ? malloc(count * size) : NULL;
+    return mul_overflow(count, size, &size) ? NULL : malloc(size);
 }
 
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