Description:
------------
When using OCILob->read(length) function with BLOBs containing 0's it reads specified amount of bytes but doesn't move internal pointer properly. The pointer is moved to the next '0' byte and no further. 
I think the possible cause of this bug is line 223 in oci8_lob.c file:
data_len_chars = OCIMultiByteStrnDisplayLength(connection->env, *data, bytes_total); 

Propably the function quits after reaching '\0' character instead of checking bytes_total bytes and as such should be used only with CLOBs.

Reproduce code:
---------------
First 128 bytes in the BLOB I'm reading are 0's, then there are 5 non-zero bytes followed by some more 0's.

$stmt = oci_parse($auth->conn, "SELECT ZDJT_IMAGE FROM IMAGES WHERE IMAGE_ID = 1");
oci_execute($stmt);
$row = oci_fetch_assoc($stmt);

$row['ZDJT_IMAGE']->read(128);
echo $row['ZDJT_IMAGE']->tell();
$row['ZDJT_IMAGE']->read(128);
echo $row['ZDJT_IMAGE']->tell();

$row['ZDJT_IMAGE']->seek(128);
echo $row['ZDJT_IMAGE']->tell();
$row['ZDJT_IMAGE']->read(128);
echo $row['ZDJT_IMAGE']->tell();


Expected result:
----------------
The expected result would be:
128
256

128
256

Actual result:
--------------
0
0

128
133