(possible) memory leak at pr_overlaps

in `prefix.c` around line 700, function pr_overlaps
```
static inline
bool pr_overlaps(prefix_range *a, prefix_range *b) {
  prefix_range *inter = pr_inter(a, b);

  return strlen(inter->prefix) > 0 || (inter->first != 0 && inter->last != 0);
}
```
it calls `pr_inter`, who `palloc` a `prefix_range` variable as intersect result, but seems to forget to `pfree` it.