Description:
------------
setting mbstring internal encoding with mb_internal_encoding() 
function gets reset at some point with 5.2.10, and mb_strtolower() 
etc that are called without implicit charset will fail. (calling 
mb_strtolower() with 2 arguments will succeed.

in other speak, such code fails:
echo mb_internal_encoding(); -> prints ISO-8859-1
mb_internal_encoding('UTF-8');
echo mb_internal_encoding(); -> prints UTF-8
... /// some code ///
echo mb_internal_encoding(); -> prints ISO-8859-1

if i set the internal encoding via php.ini (ini_set() is fine too), 
then the problem does not occour. ie such code works ok:
echo mb_internal_encoding(); -> prints ISO-8859-1
ini_set("mbstring.internal_encoding", 'UTF-8');
echo mb_internal_encoding(); -> prints UTF-8
... /// that same code ///
echo mb_internal_encoding(); -> prints UTF-8


I have not yet able to create exact php code that is exact 
reproducer, but the same php code, input data to php script, it 
works with 5.2.9 and when reverting this commit:
http://www.mail-archive.com/php-cvs%40lists.php.net/msg40593.html

from brief looking i see that there is some inconsistency, that one 
code sets the internal encoding from php.ini and the 
mb_internal_encoding() function does not update php.ini setting.