Address some compiler warnings (Xcode 12)

* Missing prototypes
* Unused function parameters
* Float comparison in preferences

src/dialogxml/dialogs/dialog.cpp

@@ -393,9 +393,9 @@ void cDialog::loadFromFile(const DialogDefn& file){
 		}
 		if(iter->second->isContainer()){
 			cContainer* tmp = dynamic_cast<cContainer*>(iter->second);
-			tmp->forEach([this, iter](std::string key, cControl& child) {
-				if (typeid(&child) == typeid(cTextField*)) {
-					if (currentFocus.empty()) currentFocus = iter->first;
+			tmp->forEach([this, iter](std::string, cControl& child) {
+				if(typeid(&child) == typeid(cTextField*)) {
+					if(currentFocus.empty()) currentFocus = iter->first;
 				}
 			});
 		}

src/game/boe.dlgutil.cpp

@@ -1317,8 +1317,17 @@ void pick_preferences() {
 	int store_display_mode = get_int_pref("DisplayMode");
 	prefsDlog.run(std::bind(give_help, 55, 0, std::ref(prefsDlog)));
 	
+	// Suppress the float comparison warning.
+ 	// We know it's safe here - we're just comparing static values.
+	#ifdef __GNUC__
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wfloat-equal"
+	#endif
 	if(get_int_pref("DisplayMode") != store_display_mode || get_float_pref("UIScale") != ui_scale || get_float_pref("UIScaleMap") != ui_map_scale)
 		changed_display_mode = true;
+	#ifdef __GNUC__
+	#pragma GCC diagnostic pop
+	#endif
 }
 
 static void put_party_stats(cDialog& me) {

src/game/boe.main.cpp

@@ -227,7 +227,7 @@ static void init_ui() {
 	init_buttons();
 }
 
-void process_args(int argc, char* argv[]) {
+static void process_args(int argc, char* argv[]) {
 	// Command line usage:
 	//  "Blades of Exile"                               # basic launch
 	//  "Blades of Exile" <save file>                   # launch and load save file
@@ -257,7 +257,7 @@ void process_args(int argc, char* argv[]) {
 	}
 }
 
-void replay_next_action() {
+static void replay_next_action() {
 	bool did_something = false, need_redraw = false, need_reprint = false;
 
 	Element& next_action = pop_next_action();

src/game/boe.startup.cpp

@@ -136,7 +136,7 @@ void handle_splash_events() {
 	}
 }
 
-rectangle view_rect() {
+static rectangle view_rect() {
 	sf::Vector2f size = mainPtr.getView().getSize();
 	return rectangle(0, 0, size.y, size.x);
 }

src/tools/winutil.mac.mm

@@ -182,7 +182,7 @@ int getMenubarHeight() {
 	return 0;
 }
 
-void adjust_window_for_menubar(int mode, unsigned int width, unsigned int height) {
+void adjust_window_for_menubar(int, unsigned int, unsigned int) {
 }
 
 NSOpenPanel* dlg_get_scen;