1.0.44.16: ir2tran: Don't try to stack-allocate VALUE-CELLs.

1.0.44.16: ir2tran: Don't try to stack-allocate VALUE-CELLs.

  * Explicit VALUE-CELLs are only used if a closure that refers
to a mutable LAMBDA-VAR has indefinite extent, implying that the
reference itself has indefinite extent.  In such cases, dynamic
extent allocation of the VALUE-CELL is contraindicated.

  * Remove most of the logic from EMIT-MAKE-VALUE-CELL, leaving
only the statistics-tracking (EVENT) and the VOP emission,
forcing the new VALUE-CELL to be heap-allocated.