Marloss tweaks

Small package of tweaks:
* Colors fungal blossoms cyan, so you can tell them apart from trees
* Changes fungal-flowers symbol to cyan T, from grey F
* Fungal haze now has a nontrivial chance to convert TREE/YOUNG terrain to more fungal blossoms
* Fungal haze is now marginally more infectious
* Fungal haze now checks for gas mask or equivalent for dangerous-field purposes, as intended