Problems with r189

[sir_nacnud]

I got a compile error on Linux.  #include <string> needs to be added to RuleSet.h.

I also noticed a warning with SavedBattleGrame.cpp, _terrian needs to be the first variable initialized in the constructor.

Lastly I ran into a problem where terrain data was failing to load due to case sensitive filenames.

The attached patch fixes all of these issues.

[zear]

I confirm this problem occurs on my linux machine and that this patch fixes it.
Thanks sir_nacnud

[Daiky]

I'm doing some cleanup in the battlescape code, so I'll add this one, thanks.