Work in progress to replace /etc/security, not yet linked to the build.

Main design goals:
1. Safely handle untrusted file names and file content.
2. Output compatibility with current security(8) to please people
parsing the output with scripts (except when improving functionality
right away saves considerable implementation effort). Substantial
functional enhancements are for later.

Prodding to do this in Perl by deraadt@.
Using some feedback from espie@.

Agree to put this in now and at this place even though only about
one third of the functionality is ready, to complete it in the tree:
beck@ espie@ millert@ deraadt@