Gets the integer value stored inside a node.
If the node holds a double value, its integer component is returned.
If the node holds a `FALSE` boolean value, `0` is returned; otherwise, a non-zero integer is returned.
If the node holds a `JSON_NODE_NULL` value or a value of another non-integer type, `0` is returned.
| this |
a node holding an integer |
|
an integer value. |