+;;; Create and return a breakpoint. When program execution encounters
+;;; the breakpoint, the system calls HOOK-FUNCTION. HOOK-FUNCTION takes the
+;;; current frame for the function in which the program is running and the
+;;; breakpoint object.
+;;;
+;;; WHAT and KIND determine where in a function the system invokes
+;;; HOOK-FUNCTION. WHAT is either a code-location or a debug-function.
+;;; KIND is one of :CODE-LOCATION, :FUNCTION-START, or :FUNCTION-END.
+;;; Since the starts and ends of functions may not have code-locations
+;;; representing them, designate these places by supplying WHAT as a
+;;; debug-function and KIND indicating the :FUNCTION-START or
+;;; :FUNCTION-END. When WHAT is a debug-function and kind is
+;;; :FUNCTION-END, then hook-function must take two additional
+;;; arguments, a list of values returned by the function and a
+;;; FUNCTION-END-COOKIE.
+;;;
+;;; INFO is information supplied by and used by the user.
+;;;
+;;; FUNCTION-END-COOKIE is a function. To implement :FUNCTION-END
+;;; breakpoints, the system uses starter breakpoints to establish the
+;;; :FUNCTION-END breakpoint for each invocation of the function. Upon
+;;; each entry, the system creates a unique cookie to identify the
+;;; invocation, and when the user supplies a function for this
+;;; argument, the system invokes it on the frame and the cookie. The
+;;; system later invokes the :FUNCTION-END breakpoint hook on the same
+;;; cookie. The user may save the cookie for comparison in the hook
+;;; function.
+;;;
+;;; Signal an error if WHAT is an unknown code-location.