#961: Do not rely on $_POST['redirect_url'].
#961: Refactor code - create a new validate_redirect() function.
#990: Fix security vulnerability in profile.php.
Escape output of emails in admin panel.

Related to #990.
Update version number to 1.5.7.
Strict type comparison.
Merge branch 'master' into 1.5-next

Conflicts:
	login.php