1.0.6.59: bogus metacircles due to interrupted applicable method comp.

1.0.6.59: bogus metacircles due to interrupted applicable method comp.

 * If an interrupt arrives while have stuff on the *CACHE-MISS-VALUES-STACK*
   and the interrupt handler happens to call a gf that is already there,
   we used to think this was a metacircle. Instead we need to bind
   variables like this to "empty" values for interrupt hanlers.

 * Test.

 * Note some bugs.