Eliminate long SMARTLIST_FOREACH statements
I introduced SMARTLIST_FOREACH_{BEGIN,END} a while back so that we wouldn't have the attendant problems from having large SMARTLIST_FOREACH() blocks. But there are still some of those lingering in the codebase.
I propose a 10-line maximum for a SMARTLIST_FOREACH statement, and that we prohibit them from nesting.
I was going to do this on 0.2.3, but I realize that if somebody else proposed doing this on 0.2.3 I would say "no", so this is 0.2.4 material.