Add st_blocks binding

As `stat(2)` states on my system, there is a field `st_blocks` in `struct stat`, which represents

> The actual number of blocks allocated for the file in 512-byte units. As short symbolic links are stored in the inode, this number may be zero.

For sparse files, this size may differ significantly from `st_size` (`fileSize` here), which represents apparent/logical/virtual file size.

`st_size` is needed for implementing a `du`-like utility.

Please bind this field too.