v0.13.4

• ENDPOINT PING was wrong on any host without unprivileged ICMP sockets:
  the raw socket sees every reply on the host, and the matcher only checked
  the sequence number, so a parallel scan mixed endpoints' replies together.
  Measured on OpenWrt: a Frankfurt endpoint 41ms away reported 6-32ms and a
  2ms one reported 0.09ms. Now the source address has to match too.
• the latest-version check caches its answer in the temp dir instead of
  ~/.cache, which on OpenWrt is the flash overlay.

Commits

• fix: drop host ping replies that came from another endpoint (8ec2902)
• fix: cache the latest-version answer in the temp dir, not on flash (073baf7)