Merge pull request #50 from daurnimator/master

Misc commits
remove test as ok to have ulimit set
syscall/linux/types: Only copy data if it exists
syscall/linux/types: Use tonumber in cmsg:datalen()
Merge pull request #51 from daurnimator/patch-1

syscall/linux/types: Only copy data if it exists
Merge pull request #52 from daurnimator/patch-2

syscall/linux/types: Use tonumber in cmsg:datalen()
return -1 for rlimit not the rather long hex value
allow -1 for rlimit
cleanup, notes
gitignore core files
gitignore ktrace files
syscall/linux/nl: Rewrite tbuffer to be based on a nicer function `align_types`
syscall/linux/nl: Use `align_types` directly in `ifla_f`
syscall/linux/types: Add `fds` and `credentials` methods to cmsg