Various field/belt related stuff

- Remove all field booleans except quickfire and belt, which have been moved to cCurTown
- Alter and extend place_spell_pattern, to allow arbitrary damage types and to make it more clear in the code what's happening when it's called
- Delete fields.cpp file; a few things moved to locutils.cpp, but most are now part of cCurTown
- set_terrain function automatically updates belt present boolean if setting to a conveyor.

osx/boe.main.cpp

@@ -13,7 +13,7 @@
 #include "boe.text.h"
 #include "boe.party.h"
 #include "boe.items.h"
-#include "boe.fields.h"
+#include "boe.locutils.h"
 #include "boe.town.h"
 #include "boe.startup.h"
 #include "boe.dlgutil.h"
@@ -135,10 +135,6 @@ short store_current_pc = 0;
 
 sf::Clock animTimer;
 
-// Special stuff booleans
-bool web,crate,barrel,fire_barrier,force_barrier,quickfire,force_wall,fire_wall,antimagic,scloud,ice_wall,blade_wall;
-bool sleep_field;
-
 //
 //	Main body of program Exile
 //