NCONC type derivation

[Nikodemus Siivola]

(NCONC 42) => 42 ; this is specified and correct.

Unfortunately the knowledge of the compiler ends with the declaration:

NCONC names a compiled function:
  Lambda-list: (&REST LISTS)
  Declared type: (FUNCTION * (VALUES T &OPTIONAL))
  Documentation:
    Concatenates the lists given as arguments (by changing them)
  Source file: SYS:SRC;CODE;LIST.LISP

...we can do better than this.

[Stas Boukarev (stassats)]

In f32ee7df37cdc62596e849c079f365000424a712