Add documentation for lots of the "undocumented" bits

In the Guile Documenta generated documentation.

knots.scm

@@ -105,6 +105,8 @@ wait on CVAR in a fiber to implement clean shutdown on Ctrl-C:
             (sigaction SIGINT #f))))))
 
 (define (call-with-temporary-thread thunk)
+  "Run THUNK in a temporary thread and return its result to the
+calling fiber."
   (let ((channel (make-channel)))
     (call-with-new-thread
      (lambda ()