Description:
------------
htmlspecialchars() / htmlentities() returns incorrect results when an 
Unicode character whose codepoint is outside the range of BMP.

Confirmed with 5.3.0, 5.3SVN.


Reproduce code:
---------------
<?php
// U+1003C
var_dump(bin2hex(htmlspecialchars("\xf0\x90\x80\xbc", ENT_QUOTES, 'UTF-8'));
?>

Expected result:
----------------
string(8) "f09080bc"


Actual result:
--------------
string(8) "266c743b"