clouseau: properly remove the first element of a list
clouseau: properly remove the first element of a list

Removing an element from a list is achieved in one of two ways
depending on whether the element is the first element in the list:

* If the element is not the first element, set the CDR of the
  predecessor CONS cell to the successor CONS cell (cutting out the
  element's CONS cell).

* If the element is the first element and the place in which the whole
  list resides is mutable, set the value of the place to the CDR of the
  element's CONS cell (removing the first CONS cell of the list).

If removing the element is not possible, indicate that fact properly.

slyrus/mcclim,slyrus/mcclim