1.0.16.39: small lisp-side interrupt handling improvements

1.0.16.39: small lisp-side interrupt handling improvements

 * In INVOKE-INTERRUPTION, disable interrupts before doing the interrupt
   handler bindings -- no point in making the window for recursive interrupts
   any bigger then it already is.

 * Similarly, ALLOW-WITH-INTERRUPTS only after the *STACK-TOP-HINT*
   has been computed. (Actually, the stack top hint computation should
   not be done for all interrupts, instead it would be better to add
   an argument to indicate we want to start from the interrupted frame
   to MAP-BACKTRACE.)

 * Declare the &REST argument of (FLET RUN-HANDLER) dynamic extent.