Correct header read/write for 32bit

[drystone]

Change 64bit reads/writes to 32bit for 32bit data files:

gdbm-native-rs/src/header.rs

Lines 47 to 59 in a256a87

	// fixme: read u32, not u64, if is_lfs
	let magic = Magic::from_reader(reader)?;
	let block_sz = read32(magic.endian(), reader)?;
	let dir_ofs = read64(magic.endian(), reader)?;
	let dir_sz = read32(magic.endian(), reader)?;
	let dir_bits = read32(magic.endian(), reader)?;
	let bucket_sz = read32(magic.endian(), reader)?;
	let bucket_elems = read32(magic.endian(), reader)?;
	let next_block = read64(magic.endian(), reader)?;
	let avail_sz = read32(magic.endian(), reader)?;
	let avail_count = read32(magic.endian(), reader)?;
	let avail_next_block = read64(magic.endian(), reader)?;