Description:
------------
trying to read large database objects (>64K) via PDO from an informix database via a stream causes a crash of the php executable 


Reproduce code:
---------------
$query=$dbh->query("select * from large ");
$row=$query->fetch(PDO::FETCH_ASSOC);
while ( $row ) {
        $file = fopen ("/tmp/large.photo.$count","w");
        $test=fread($row["PHOTO"],20000);
        while($test) {
                fwrite ( $file, $test) ;
                $test=fread($row["PHOTO"],20000);
        }
        fclose ( $file);
}



Expected result:
----------------
an error in case of misprogramming.

Actual result:
--------------
#0  0x007933dc in memcpy () from /lib/tls/libc.so.6
#1  0x081db395 in _php_stream_read (stream=0x97a4ffd, buf=0x9794d3d "",
    size=3219790640)
    at /home/php/main/streams/streams.c:618
#2  0x08180fa3 in zif_fread (ht=2, return_value=0x9760b6c,
    return_value_ptr=0x0, this_ptr=0x0, return_value_used=1)
    at /home/php/ext/standard/file.c:1811
#3  0x082192ec in zend_do_fcall_common_helper_SPEC (execute_data=0xbfeaa650)
    at /home/php/Zend/zend_vm_execute.h:192