Grace period needed for meteors

[bcmcms]

Though this is a rare event, I can now personally attest that I have spawned into an expedition, progressed 1 tic of time, and immediately gotten vaporized by a random meteor. A small window of spawn invulnerability seems like it would prevent this, and I believe it should; dying instantly on expedition doesn't seem like good gameplay.

In normal CDDA meteors strike when map chunks load in, which is always at the edge of your screen, so you can't really get hit by one. Sky Islands teleports people to random map locations though, so this is a unique issue for the mod.