The code appending new configuration entries to our current list first
allocates the `cvar` structure and then passes it to `append_entry`. As
we want to extend `append_entry` to store configuration entries in a map
as well as in a list for ordered iteration, we will have to create two
`cvar` structures, though. As such, the future change will become much
easier when allocation of the `cvar` structure is doen in `append_entry`
itself.