Converts an integer literal of type :int to an OCaml number.
DESCRIPTION
The call dest_intconst t where t is a canonical integer literal of type
:int, returns the corresponding OCaml number (type num). The permissible
forms of integer literals are `&n' for a numeral n or `-- &n' for a
nonzero numeral n.
FAILURE CONDITIONS
Fails if applied to a term that is not a canonical integer literal of type
:int.
EXAMPLE
# dest_intconst `-- &11 :int`;;
val it : num = -11