Slowdown in EVAL

[MasterDuke17]

@Juerd has a test file for his MQTT::Client module (https://github.com/Juerd/p6-mqtt/blob/master/t/regex.t) that he uses as a benchmark canary. 1c101a0 causes it to take about twice as long. On @AlexDaniel's server, before that commit it took ~5s, after that commit it was something >7.5s. @niner any thoughts?

[niner]

I'd guess it's because the World of each of these EVALs now has it's own quote_lang_cache. If that's the reason, you should see a lot of time spent in con_lang