Detect incorrect ACL (allow without deny)

When a configuration block contains allow directive with some IP address or subnet, it most likely should also contain "deny all" directive (or it should be enforced somewhere else). Otherwise, there's basically no access limitation. Probably it's a good idea to detect such vulnerable configurations.

Example:

location / {
      root /var/www/;
      allow 10.0.0.0/8;
      . . .
}