Fix build breakage of Mac Cocoa app.

cpp/src/SynthApp.xcodeproj/project.pbxproj

@@ -3,7 +3,7 @@
 	archiveVersion = 1;
 	classes = {
 	};
-	objectVersion = 45;
+	objectVersion = 46;
 	objects = {
 
 /* Begin PBXBuildFile section */
@@ -182,7 +182,14 @@
 			};
 			buildConfigurationList = F2D5F35CD2FF169326ADC8E8 /* Build configuration list for PBXProject "SynthApp" */;
 			compatibilityVersion = "Xcode 3.2";
+			developmentRegion = English;
 			hasScannedForEncodings = 1;
+			knownRegions = (
+				English,
+				Japanese,
+				French,
+				German,
+			);
 			mainGroup = 56669AEF9C728CE587C3E8A3;
 			projectDirPath = "";
 			projectReferences = (

cpp/src/sin.cc

@@ -16,6 +16,7 @@
 
 #include <math.h>
 
+#include "synth.h"
 #include "sin.h"
 
 #define R (1 << 29)