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/pcedit/pc.graphics.cpp

@@ -13,8 +13,6 @@
 #include "message.h"
 #include "mathutil.h"
 
-extern std::string get_str(std::string, short);
-
 extern cUniverse univ;
 
 extern sf::RenderWindow mainPtr;
@@ -229,7 +227,6 @@ void init_main_buttons()
 
 void Set_up_win ()
 {
-	short i;
 	title_gworld.loadFromImage(*ResMgr::get<ImageRsrc>("pcedtitle"));
 	invenbtn_gworld.loadFromImage(*ResMgr::get<ImageRsrc>("invenbtns"));
 	status_gworld.loadFromImage(*ResMgr::get<ImageRsrc>("staticons"));
@@ -326,9 +323,9 @@ void draw_main_screen()
 	
 }
 
-void do_button_action(short which_pc,short which_button)
+// TODO: Not quite sure what the first parameter is for
+void do_button_action(short /*which_pc*/,short which_button)
 {
-	unsigned long dummy;
 
 	current_pressed_button = which_button;
 	redraw_screen();