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.actions.h

@@ -47,7 +47,6 @@ void set_up_start_screen();
 void set_up_main_screen();
 void start_town_edit();
 void start_out_edit();
-void shut_down_menus(short mode);
 void start_terrain_editing();
 void start_monster_editing(short just_redo_text);
 void start_item_editing(short just_redo_text);
@@ -62,7 +61,6 @@ bool monst_on_space(location loc,short m_num);
 void place_edit_special(location loc);
 void set_special(location spot_hit);
 bool save_check(std::string which_dlog);
-void update_item_menu();
 
 ter_num_t get_ground_from_ter(ter_num_t ter);
 bool terrain_matches(unsigned char x, unsigned char y, ter_num_t ter);