This contains tmpfs as an example fs and lseek as an example converted consumer.
Allows for unlocked retrieval of frequently used parameters (most notably size). In the current form it is suitable to use in exec as well. It is *not* yet fit for mmap due to missing va_flags, but provisions are made to allow fro growing the structure and catching filesytems which did not get updated.
New type is declared to make things less error prone.
I'm leaning towards adding an _UNLOCKED variant and removing the locked parameter. Less things to sanity check and also less error prone, albeit yet another extension to the API.