kernel: Add aligned_alloc implementation.

Needed by default with GCC 11.

src/system/kernel/slab/allocator.cpp

@@ -229,6 +229,16 @@ posix_memalign(void** _pointer, size_t alignment, size_t size)
 }
 
 
+void *
+aligned_alloc(size_t alignment, size_t size)
+{
+	if ((size % alignment) != 0)
+		return NULL;
+
+	return memalign(alignment, size);
+}
+
+
 void
 free_etc(void *address, uint32 flags)
 {