Added fluid-cell-ref and fluid-cell-set!.

scheme/interfaces.scm

@@ -394,6 +394,10 @@
 	  let-fluid
 	  let-fluids
 	  fluid
+	  
+	  fluid-cell-ref
+	  fluid-cell-set!
+
 	  set-fluid!))
 
 (define-interface fluids-internal-interface

scheme/rts/thread-env.scm

@@ -88,6 +88,14 @@
 	(loop (cddr args)
 	      (cons (cons (car args) (cadr args)) env)))))
 
+; Handy utilities.
+
+(define (fluid-cell-ref f)
+  (cell-ref (fluid f)))
+
+(define (fluid-cell-set! f value)
+  (cell-set! (fluid f) value))
+
 ; Thread cells
 
 (define-record-type thread-cell :thread-cell