GUI: U32: Convert majority of code to use U32

This commit also includes some additional major changes.

- Return U32String from TransMan getTranslation()
- Change tooltips to be U32Strings
- Remove temporary code of convertToU32String
- U32 Support various dialogs (Browser, FileBrowser, Messages, Chooser, etc)
- U32 for music plugins
- U32 for OSD messages
- Add some helper functions to ustr.cpp
- Change default tooltips from nullptr & 0 -> ""
- Some runtime exceptions may occur when changing languages due to incorrect String::Format

backends/graphics/opengl/opengl-graphics.cpp

@@ -785,7 +785,7 @@ void OpenGLGraphicsManager::setCursorPalette(const byte *colors, uint start, uin
 	updateCursorPalette();
 }
 
-void OpenGLGraphicsManager::displayMessageOnOSD(const char *msg) {
+void OpenGLGraphicsManager::displayMessageOnOSD(const Common::U32String &msg) {
 #ifdef USE_OSD
 	_osdMessageChangeRequest = true;
 
@@ -796,8 +796,8 @@ void OpenGLGraphicsManager::displayMessageOnOSD(const char *msg) {
 #ifdef USE_OSD
 void OpenGLGraphicsManager::osdMessageUpdateSurface() {
 	// Split up the lines.
-	Common::Array<Common::String> osdLines;
-	Common::StringTokenizer tokenizer(_osdMessageNextData, "\n");
+	Common::Array<Common::U32String> osdLines;
+	Common::StringTokenizer tokenizer(Common::convertFromU32String(_osdMessageNextData), "\n");
 	while (!tokenizer.empty()) {
 		osdLines.push_back(tokenizer.nextToken());
 	}
@@ -857,7 +857,7 @@ void OpenGLGraphicsManager::osdMessageUpdateSurface() {
 			ConfMan.getBool("tts_enabled", "scummvm")) {
 		Common::TextToSpeechManager *ttsMan = g_system->getTextToSpeechManager();
 		if (ttsMan)
-			ttsMan->say(_osdMessageNextData);
+			ttsMan->say(Common::convertFromU32String(_osdMessageNextData));
 	}
 #endif // USE_TTS
 	// Clear the text update request