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/classes/town.cpp

@@ -14,9 +14,9 @@
 #include "classes.h"
 #include "oldstructs.h"
 
-void cTown::append(legacy::big_tr_type& old){}
-void cTown::append(legacy::ave_tr_type& old){}
-void cTown::append(legacy::tiny_tr_type& old){}
+void cTown::append(legacy::big_tr_type&){}
+void cTown::append(legacy::ave_tr_type&){}
+void cTown::append(legacy::tiny_tr_type&){}
 
 cTown& cTown::operator = (legacy::town_record_type& old){
 	int i;
@@ -82,7 +82,7 @@ cTown& cTown::operator = (legacy::town_record_type& old){
 cTown::cTown(){}
 
 short max_dim[3] = {64,48,32};
-cTown::cTown(short size){
+cTown::cTown(short){
 	short i,s;
 	location d_loc(100,0);
 	cTown::cWandering d_wan = {0,0,0,0};