apl: ? roll/random + apl-rng-seed! (+4 tests)

apl-rng-state global mutable LCG.
apl-rng-seed! for deterministic tests.
apl-rng-next! advances state.
apl-roll: monadic ?N returns scalar in 1..N (apl-io-relative).

apl-monadic-fn dispatches "?" → apl-roll.

apl-run "?10" → 8 (with seed 42)
apl-run "?100" → in 1..100

lib/apl/runtime.sx

@@ -1004,6 +1004,28 @@
         (some (fn (c) (= c 0)) codes)
         (some (fn (c) (= c (nth e 1))) codes)))))
 
+(define apl-rng-state 12345)
+
+(define apl-rng-seed! (fn (s) (set! apl-rng-state s)))
+
+(define
+  apl-rng-next!
+  (fn
+    ()
+    (begin
+      (set!
+        apl-rng-state
+        (mod (+ (* apl-rng-state 1103515245) 12345) 2147483648))
+      apl-rng-state)))
+
+(define
+  apl-roll
+  (fn
+    (arr)
+    (let
+      ((n (if (scalar? arr) (first (get arr :ravel)) (first (get arr :ravel)))))
+      (apl-scalar (+ apl-io (mod (apl-rng-next!) n))))))
+
 (define
   apl-cartesian
   (fn