Multiple evaluation of the function argument, oops.

  Add bunch of missing symbols to the manual, and go over several
  docstrings reformatting them for the benefit of the documentation
  generator.

  (A crapton of symbols are still not in the manual.)

Added new test cases for DISJOIN, CONJOIN, COMPOSE and MULTIPLE-VALUE-COMPOSE.
All of them testing for the edge case of a single predicate / function.

	* functions.lisp: Make optimization notes about
	%COERCE-CALLABLE-TO-FUN go away by inserting calls to
	ENSURE-FUNCTION to the appropriate places.

Added:
 * XOR
 * WHICHEVER
 * SWITCH, ESWITCH, CSWItCH
 * UNIONF, NUNIONF
 * ALIST-PLIST, PLIST-ALIST
 * ENSURE-CONS
 * NAMED-LAMDBA
 * DEFINE-CONSTANT
 * STRING-DESIGNATOR

Note:
 Documentation strings of many new operators are sorely lacking, particularly
 NAMED-LAMBDA and *SWITCH.