Replace the dummy-use var in SMARTLIST_FOREACH_END() with one that is less likely...

Replace the dummy-use var in SMARTLIST_FOREACH_END() with one that is less likely to confuse analysis tools into thinking we do use after free.  Arguably, (void)x should count as use in suppressing unused variable warnings, but not in generating hey-you-used-a-variable warnings.  Arguably, though, it shouldn't.

svn:r16815