SLUDGE: Fix Missing Default Switch Cases

These are flagged by GCC if -Wswitch-default is enabled.

engines/sludge/builtin.cpp

@@ -82,6 +82,8 @@ bool failSecurityCheck(const Common::String &fn) {
 			case '|':
 				fatal("Filenames may not contain the following characters: \n\n\\  /  :  \"  <  >  |  ?  *\n\nConsequently, the following filename is not allowed:", fn);
 				return true;
+			default:
+				break;
 		}
 	}
 	return false;
@@ -123,6 +125,9 @@ static BuiltReturn sayCore(int numParams, LoadedFunction *fun, bool sayIt) {
 			//debugOut ("BUILTIN: sayCore: %s (%i)\n", newText, p);
 			fun->isSpeech = true;
 			return BR_KEEP_AND_PAUSE;
+
+		default:
+			break;
 	}
 
 	fatal("Function should have either 2 or 3 parameters");

engines/sludge/fileset.cpp

@@ -182,6 +182,9 @@ Common::String ResourceManager::convertString(const Common::String &s) {
 				// falls through
 			case 1:
 				r = wc + r;
+				break;
+			default:
+				break;
 		}
 		res += r;
 	}

engines/sludge/transition.cpp

@@ -403,7 +403,8 @@ void GraphicsManager::fixBrightness() {
 		case 6:
 			transitionSnapshotBox();
 			break;
-
+		default:
+			break;
 	}
 }