1.0.30.33: failed aver in %ALLOCATE-CLOSURES IR2 conversion

1.0.30.33: failed aver in %ALLOCATE-CLOSURES IR2 conversion

 Patch by Larry D'Anna. He explains:

   This snippit
      (labels ((K (&optional x) #'k)))
   fails with failed AVER: (XEP-P XEP), in %ALLOCATE-CLOSURES-IR2-CONVERT-OPTIMIZER

   The problem is that it's trying to allocate a closure for the XEP
   for K, but K has been deleted because nothing references K except
   itself. %ALLOCATE-CLOSURES-IR2-CONVERT-OPTIMIZER already skips any
   leafs that lacks a XEP. This patch makes it also skip leafs who's
   XEPs have been deleted.