Nuke as many warnings as possible, and several globals as well

- Warnings completely suppressed for the included TinyXML and gzstream libraries
- Parentheses warnings are now errors, since there were several that looked like bugs
- Ditto for dangling else warnings

Some of these warnings were actually bugs:
- Town wandering monsters would have never spawned, because the code to do so was accidentally nested within a check for overall_mode == MODE_OUTDOORS
---> boe.monster.cpp, lines 105-137
- Monster's behaviour with respect to elemental fields did not correctly depend on their immunities (this is the same precedence issue Sylae messed up fixing in the Windows code)
---> boe.monsters.cpp, lines 345-359
- Display of damage blocked by armour appeared to be incorrect (needs verification)
---> boe.newgraph.cpp, line 1079
- Three-choice dialogs probably weren't dealing with unusual button types correctly, though that's a minor point since they aren't expected to use such buttons

osx/boe.fileio.cpp

@@ -189,7 +189,7 @@ void finish_load_party(){
 					force_barrier = true;
 				if (univ.town.is_quickfire(j,k) == true)
 					quickfire = true;
-				if ((scenario.ter_types[univ.town->terrain(j,k)].special == TER_SPEC_CONVEYOR))
+				if(scenario.ter_types[univ.town->terrain(j,k)].special == TER_SPEC_CONVEYOR)
 					belt_present = true;
 			}
 		force_wall = true;