render tunnel=cave like tunnel=yes

[matkoniecz]

This is rather obvious value for mapping tourist route through cave, but this is currently discouraged by this style.

tunnel=cave is currently almost completely unused, but at least in part it is caused by default style refusing to consider path with tunnel=cave as a tunnel - see http://www.openstreetmap.org/?mlat=50.17483&mlon=19.80719#map=17/50.17483/19.80719 for example of ways that I tagged as tunnel=yes instead of tunnel=cave, due to this problem

see also #182 ("Support all values of tunnel tag instead of just tunnel=yes")

[matthijsmelissen]

Tunnel=cave only has 8 occurrences. I'm also not a fan of the tunnel=* tagging scheme, it makes it a lot harder for renderers to interpret the data (especially without using catch-all rendering). I will therefore close this issue.