Method lazyvec_skeleton() generates a full sample implementation

[MarcusKlik]

To create a custom ALTREP vector, method lazyvec() needs overrides for methods from the ALTREP API. For the average user, it will take some time to study this API to get a custom vector operational. To facilitate this, sample implementations can be created using lazyvec_skeleton(). Samples for each type should be available. The user can tailor the generated code to create a custom ALTREP vector:

• integer: sample implementation of an ALTREP integer range
• double: sample implementation of an ALTREP real range
• logical: sample implementation of an ALTREP (factor 16) compressed logical vector (using bitWAnd())
• raw: sample implementation of an ALTREP file based out-of-memory raw vector
• character: sample implementation of an ALTREP as.character(n:m)
• integer: a wrapper around an existing ALTREP (much like lazyvec's listener

[MarcusKlik]

These samples will be explained in vignettes and on the website.