o Code simplification and refactoring:
    - Do not allow the body of any SMARTLIST_FOREACH block to exceed
      10 lines.  Doing so in the past has led to hard-to-debug code.
      The new style is to use the SMARTLIST_FOREACH_{BEGIN,END} pair.
    - Do not allow SMARTLIST_FOREACH blocks to nest. Any nested block
      ought to be using SMARTLIST_FOREACH_{BEGIN,END}.