polling mirror for dump blocks event loop

[MartinNowak]

Makes code-mirror.dlang.io unresponsive for several minutes every 30min. Should be run as a background task instead.

[s-ludwig]

Hm, that's strange. During the update there is lot's of network activity going on, so the event loop shouldn't be blocked. The HTTP server is running in the background, as well as the update, so there is also no way those would directly block each other. Could it be that the system is swapping and is unresponsive as a whole? That is what unfortunately still happens on the main system currently.

[WebFreak001]

try compiling with --override-config vibe-d:core/libevent, makes everything work well again. Had that issue in another project.