Add $switch CPS term kind

* module/language/cps.scm ($switch): New term.
* doc/ref/compiler.texi (CPS in Guile): Add documentation.

* module/language/cps.scm (build-term, parse-cps, unparse-cps)
* module/language/cps/closure-conversion.scm (compute-non-operator-uses)
  (compute-singly-referenced-labels, rewrite-shared-closure-calls)
  (compute-free-vars, convert-one)
* module/language/cps/compile-bytecode.scm (compile-function)
* module/language/cps/contification.scm (compute-singly-referenced-labels)
  (compute-contification-candidates, apply-contification)
* module/language/cps/cse.scm (compute-truthy-expressions)
  (forward-cont, term-successors, eliminate-common-subexpressions-in-fun)
* module/language/cps/dce.scm (compute-known-allocations)
  (compute-live-code, process-eliminations)
* module/language/cps/devirtualize-integers.scm (compute-use-counts)
  (peel-trace)
* module/language/cps/effects-analysis.scm (compute-effects)
* module/language/cps/licm.scm (hoist-one, hoist-in-loop)
* module/language/cps/loop-instrumentation.scm (compute-loop-headers)
* module/language/cps/peel-loops.scm (rename-cont)
* module/language/cps/renumber.scm (sort-labels-locally, renumber)
* module/language/cps/rotate-loops.scm (rotate-loop)
  (rotate-loops-in-function)
* module/language/cps/self-references.scm (resolve-self-references)
* module/language/cps/simplify.scm (compute-singly-referenced-vars)
  (eta-reduce, compute-singly-referenced-labels, beta-reduce)
* module/language/cps/slot-allocation.scm (compute-defs-and-uses)
  (add-prompt-control-flow-edges, compute-var-representations)
* module/language/cps/specialize-numbers.scm (compute-significant-bits)
* module/language/cps/split-rec.scm (compute-free-vars)
* module/language/cps/type-fold.scm (local-type-fold)
* module/language/cps/types.scm (successor-count, infer-types)
* module/language/cps/utils.scm (compute-function-body)
  (compute-successors, compute-predecessors)
* module/language/cps/verify.scm (compute-available-definitions)
  (check-valid-var-uses, check-arities): Add support for new term.

module/language/cps/compile-bytecode.scm

@@ -621,6 +621,12 @@
          (compile-test label (skip-elided-conts (1+ label))
                        (forward-label kf) (forward-label kt)
                        op param args))
+        (($ $switch kf kt* src arg)
+         (when src
+           (emit-source asm src))
+         (emit-jtable asm (from-sp (slot arg))
+                      (list->vector (map forward-label
+                                         (append kt* (list kf))))))
         (($ $prompt k kh src escape? tag)
          (when src
            (emit-source asm src))