Description:
------------
msql_fetch_row() and msql_fetch_array() silently drop columns that contain NULL values.  It's important to retrieve all data from a row, even if it's NULL.  oci8 does this just fine.

While there's a comment in the msql_fetch_array() documentation to watch out for items that have NULL/0/'' values, it doesn't exactly say what the problem is and it only talks about results that have only one column.

Reproduce code:
---------------
$con = msql_connect();
$db  = msql_select_db('ptdb', $con);
msql_query('CREATE TABLE blah (i INT, c CHAR(5))', $con);
msql_query("INSERT INTO blah VALUES (1, 'a')", $con);
msql_query("INSERT INTO blah VALUES (2, NULL)", $con);
msql_query("INSERT INTO blah VALUES (NULL, 'c')", $con);
$result = msql_query('SELECT * FROM blah', $con);
while ($arr = msql_fetch_array($result, MSQL_ASSOC)) {
    var_dump($arr);
    echo "\n";
}
msql_query('DROP TABLE blah', $con);

Expected result:
----------------
array(2) {
  ["i"]=>
  string(1) "1"
  ["c"]=>
  string(1) "a"
}

array(2) {
  ["i"]=>
  string(1) "2"
  ["c"]=>
  NULL
}

array(2) {
  ["a"]=>
  NULL
  ["c"]=>
  string(1) "c"
}

Actual result:
--------------
array(2) {
  ["i"]=>
  string(1) "1"
  ["c"]=>
  string(1) "a"
}

array(1) {
  ["i"]=>
  string(1) "2"
}

array(1) {
  ["c"]=>
  string(1) "c"
}