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/scenedit/scen.fileio.cpp

@@ -585,7 +585,7 @@ void create_basic_scenario() {
 }
 
 // if which_town is -1, load town from base
-void import_town(short which_town,fs::path temp_file_to_load) {
+void import_town(short /*which_town*/,fs::path /*temp_file_to_load*/) {
 	giveError("Town import currently disabled.");
 	//	short i,j,k,l,file_id;
 	//	bool file_ok = false;
@@ -743,8 +743,8 @@ void import_town(short which_town,fs::path temp_file_to_load) {
 }
 
 // When this is called, the current town is the town to make town 0. 
-void make_new_scenario(const char* file_name,short out_width,short out_height,short making_warriors_grove,
-					   short use_grass) {
+void make_new_scenario(const char* /*file_name*/,short /*out_width*/,short /*out_height*/,short /*making_warriors_grove*/,
+					   short /*use_grass*/) {
 	//	short i,j,k,num_outdoors;
 	//	FSSpec dummy_file;
 	//	NavReplyRecord reply;