dmemcache_stats() notice

I ran into the same issue this morning running latest 7.x-1.x. My memcache servers returned a key "libevent" with value "2.0.0-stable" (or something along those lines), and the dmemcache_stats() function was attempting to aggregate it because "libevent" wasn't explicitly listed in $no_aggregate.

The attached patch adds a check for is_numeric() alongside !in_array($no_aggregate), since there's no point in attempting to sum two non-numbers. Another possible approach is to add "libevent" to the $no_aggregate array.

Hope this helps!

Patch for 8.x-2.0, adding 'libevent' to the no aggregation array.

If we simply check if it's integer, we can completely get rid of the no_aggregation array (and maybe avoid similar regressions in the future).