Description:
------------
appending a stream filter to a stream that has already had data read into its buffer can cause unfiltered data to be read back in.  This is because the data is written to writepos, but read from readpos, and so the buffer should be invalidated (writepos/readpos set to 0) prior to writing back the filtered data.

This bug affects all PHP versions, and will be fixed in 5.2, 5.3, and 6.0 by me, I have a working patch ready to commit momentarily

This bug was causing ext/phar/tests/zip/badalias.phpt to fail

Reproduce code:
---------------
execute within php5/ext/phar/tests/zip:

<?php
$a = fopen(dirname(__FILE__) . '/files/' . "badalias1.phar.zip", 'rb');
fseek($a, 37); // seek to zip header
$b = fread($a, 30);
fseek($a, 82); // seek to file data
stream_filter_append($a, 'zlib.inflate', STREAM_FILTER_READ);
var_dump(fread($a, 8));
?>


Expected result:
----------------
string(8) "hi/there"


Actual result:
--------------
string(8) "&#65533;&#65533;&#65533;/&#65533;H-J"