sanitizing ldap search. I think, in this case it only prevents ldap search

sanitizing ldap search. I think, in this case it only prevents ldap search
errors. Backend does not enclose search in () and custom search options
can't be inserted. If I am wrong, attacker was able to scrap some complex
cn=*something* search expression, that could abuse ldap backend or ldap
server.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@8894 7612ce4b-ef26-0410-bec9-ea0150e637f0