1.0.6.36: ALLOW-WITH-INTERRUPTS and interrupt safe WITH-MUTEX &co

1.0.6.36: ALLOW-WITH-INTERRUPTS and interrupt safe WITH-MUTEX &co

 * Remove the *IN-INTERRUPTION* kludge, and replace it with a
   general-purpose mechanism.

 * New variable: *ALLOW-WITH-INTERRRUPTS*. WITH-INTERRUPTS is a no-op
   unless it is true and interrupts are inhibited.

 * WITHOUT-INTERRUPTS binds *ALLOW-WITH-INTERRUPTS* to NIL, and
   establishes ALLOW-WITH-INTERRUPTS and WITH-LOCAL-INTERRUPTS as
   local macros.

   ALLOW-WITH-INTERRUPTS binds *ALLOW-WITH-INTERRUPTS* to the value it
   held before entry to WITHOUT-INTERRUPTS.

   WITH-LOCAL-INTERRUPTS is equivalent to
     (allow-with-interrups (with-interrupts ...))
   but somewhat more efficient.

 * Use the above to make WITH-MUTEX &co interrupt-safe, but still
   interruptible: WITH-FOO becomes
     (without-interrupts
       (unwind-protect
           (when (setf foo (allow-with-interrupts (get-foo)))
             (with-local-interrupts ...))
         (when foo
           (release-foo foo))))
   and GET-FOO wraps it's waiting section inside a WITH-INTERRUPTS.

 * While at it, rewrite WITH-MUTEX &co to use CALL-WITH-FOO style
   expansions.

 * Write CALL-WITH-SYSTEM-MUTEX as a more efficient alternative to:

     (without-interrupt (with-mutex ...)) ; and
     (without-gcing (with-mutex ...))

   Similarly for CALL-WITH-RECURSIVE-SYSTEM-SPINLOCK, for the benefit
   of PCL.

 * No need to signal a WARNING for WITH-INTERRUPTS inside a WITHOUT-GCING,
   as *ALLOW-WITH-INTERRUPTS* is always false there, so interrupts will
   not be enabled.