Description:
------------
Calling OCIBindByName on the same placeholder (same statement) does eat memory. The expected behaviour should be to just replace the old placeholder variable with the new one, without any new memory allocation needed.

Reproduce code:
---------------
<?
  // http://download-west.oracle.com/docs/cd/B10501_01/appdev.920/a96584/oci05bnd.htm#421792
  ob_end_flush();
  ob_implicit_flush(1);

  $conn = OCILogon("scott", "tiger", "database");
  $stmt = OCIParse($conn, "SELECT DUMMY FROM DUAL WHERE DUMMY=:DUMMY");
  $i = 1;
  while($i++) {
    OCIBindByName($stmt, ":DUMMY", &$dummy, 1);
    if ($i%500 == 0)
    echo "\rMEM -send $i: ".memory_get_usage();
  }
?>


Expected result:
----------------
The memory usage shouldn't grow.
A second call to ocibindbyname on the same placeholder should free/replace the old php internal bind variable (in oci8.c) for this placeholder...

Actual result:
--------------
actual a new bind place holder is allocated and added to the list of bind variables.

./bug.php
MEM -send 122500: 8387128
Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 20 bytes) in /user/bug.php on line 16