phpbb2.0.19 fixes security issues

re: http://www.phpbb.com/phpBB/viewtopic.php?t=352966

[Sec] fixed XSS issue (only valid for Internet Explorer) within the url bbcode
[Sec] fixed XSS issue (only valid for Internet Explorer) if html tags are allowed and enabled
[Sec] added configurable maximum login attempts to prevent dictionary attacks

Other fixes:

[Fix] corrected index on session keys table under MS SQL
[Fix] added session keys table to backup
[Fix] delete session keys entries when deleting user
[Fix] changes to support MySQL 5.0
[Fix] changes to some of the admin files to improve efficiency and remove a potential error condition when building the menu
[Fix] change truncation of username length in usercp_register.php - BFUK
[Fix] incorrect path to avatars in admin_users.php (Bug #667)
[Fix] fixed get_userdata to support correct sql escaping (non-mysql dbs) - jarnaez
[Fix] fixed captcha for those not having the zlib extension enabled
[Change] Placed version information above who is online in admin panel for better visual presence

–
Paul Laudanski, Microsoft MVP Windows-Security
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