`f:length' added

This is aggressively tested in every instance where it could be affected,
since any mishandling of this value would be incredibly dangerous (best
case, it would blow up and abort; worst case, data are interchanged between
refs).
`f:args' ignores adjacent data
`f:set-args' respects and echoes adjacent data by references

Was previously clobbered.
Assurances that all other `f:*' functions properly handle adjacent data
`arity/ref.xsl' documentation updated to reflect data adjacency guarantees
All ref functions now have data adjacency guarantees

Accessors will ignore adjacent data and mutators will echo them, by
reference, unchanged.