cs: constant tokens

Instead of allocating tokens like `undefined` or `parameter-key`
with `gensym` on startup, allocate them once for all eternity.

racket/src/cs/rumble.sls

@@ -727,8 +727,9 @@
                 record-field-accessor
                 record-field-mutator))
 
-  (define/no-lift none (chez:gensym "none"))
-  (define/no-lift none2 (chez:gensym "none2")) ; never put this in an emphemeron
+  ;; Internal tokens that are different from all possible user-level values:
+  (define/no-lift none '#{none kwcju864gpycc2h151s9atbmo-1})
+  (define/no-lift none2 '#{none kwcju864gpycc2h151s9atbmo-2}) ; never put this in an emphemeron
 
   (include "rumble/define.ss")
   (include "rumble/virtual-register.ss")

racket/src/cs/rumble/control.ss

@@ -140,7 +140,7 @@
 ;; To support special treatment of break parameterizations, and also
 ;; to initialize disabled breaks for `dynamic-wind` pre and post
 ;; thunks:
-(define break-enabled-key (gensym 'break-enabled))
+(define break-enabled-key '#{break-enabled n1kcvqw4c9hh8t3fi3659ci94-2})
 
 (define/who (continuation-prompt-available? tag)
   (check who continuation-prompt-tag? tag)

racket/src/cs/rumble/equal.ss

@@ -195,7 +195,7 @@
 ;; continuation maps `key-equality-wrap-key` to a key-wrapping
 ;; function.
 
-(define key-equality-wrap-key (gensym))
+(define key-equality-wrap-key '#{equality n1kcvqw4c9hh8t3fi3659ci94-0})
 
 ;; Looking in the continaution is expensive relative to `equal?`, so
 ;; look in a box as a quick pre-test. Multiple threads may increment

racket/src/cs/rumble/parameter.ss

@@ -1,6 +1,6 @@
 
 ;; Continuation-mark key:
-(define parameterization-key (gensym "parameterization-key"))
+(define parameterization-key '#{parameterization n1kcvqw4c9hh8t3fi3659ci94-1})
 
 (define-record parameterization (ht))
 
@@ -94,7 +94,7 @@
          [()
           (let ([c (or (parameter-cell data)
                        default-c)])
-            (thread-cell-ref c))]
+            (unsafe-thread-cell-ref c))]
          [(v)
           (let ([c (or (parameter-cell data)
                        default-c)])

racket/src/cs/rumble/thread-cell.ss

@@ -11,6 +11,9 @@
 
 (define/who (thread-cell-ref c)
   (check who thread-cell? c)
+  (unsafe-thread-cell-ref c))
+
+(define (unsafe-thread-cell-ref c)
   (let* ([t (current-engine-thread-cell-values)]
          [v (if t
                 (hashtable-ref t c none)

racket/src/cs/rumble/variable.ss

@@ -1,6 +1,6 @@
 ;; A "variable" is a linklet import or export
 
-(define undefined (gensym "undefined"))
+(define undefined '#{undefined bjjxts6iq4xqtw8kz4eb1jxbs-0})
 
 (define-record-type variable (fields (mutable val) name))