Adding a software definition for libossp-uuid

See http://www.ossp.org/pkg/lib/uuid/

This is notably useful to be able to build pgSQL with the uuid-ossp module
(http://www.postgresql.org/docs/9.1/static/uuid-ossp.html)
You should do this instead now:

```ruby
env = with_embedded_path()
env = with_standard_compiler_flags(env)
```