Hi, Guile users!

I'm working on a Guile binding to tree-sitter, an incremental parsing
library. Consider we have something like(actually taken from
tree-sitter's header file)

```
typedef struct {
  uint32_t context[4];
  const void *id;
  const TSTree *tree;
} TSNode;

uint32_t ts_node_end_byte(TSNode);
```

I'd like to write binding like

```
(pointer->procedure uint32 (dynamic-func "ts_node_end_byte" %libtree-sitter) `((,uint32 * *)))
```

As the function defined in header, we need to pass a TSNode struct by
value to ts_node_end_type. But I'm not sure how to do it in Dynamic FFI.
There's make-c-struct in (system foreign), but it'll return a pointer to
the struct.

I check the doc but can't find something useful, Can guile Dynamic FFI
pass a C struct by value or we must do it in static FFI?

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Zihao