Use fprintf rather than perror when errno won't be helpful
Document what we're doing with the @DEV header
Plug memory-leak in existing-ioctl-recording pathway
Simplify ioctl writing logic in load_ioctl
Robustify @DEV header parsing in load_ioctl
Code-style fix: whitespace before '('
Simplify ioctl_tree_with_default_device test
Add test checking load_ioctl can override the device specified in @DEV header