make cpp.NativeArray extern so its methods are always inlined (closes #2938)

std/cpp/NativeArray.hx

@@ -1,6 +1,6 @@
 package cpp;
 
-class NativeArray {
+extern class NativeArray {
 
 	public static inline function blit<T>( ioDestArray:Array<T>,
 		inDestElement:Int, inSourceArray:Array<T>,
@@ -8,13 +8,14 @@ class NativeArray {
 	untyped ioDestArray.blit(inDestElement, inSourceArray, inSourceElement, inElementCount);
 	};
 
-	public static inline function zero<T>( ioDestArray:Array<T>, ?inFirst:Int, ?inElements:Int ) {
+	public static inline function zero<T>( ioDestArray:Array<T>, ?inFirst:Int, ?inElements:Int ) : Void {
 		untyped ioDestArray.zero(inFirst, inElements);
 	};
 
 	public static inline function unsafeGet<T>( inDestArray:Array<T>, inIndex:Int) : T {
 		return untyped inDestArray.__unsafe_get(inIndex);
 	}
+
 	public static inline function unsafeSet<T>( ioDestArray:Array<T>, inIndex:Int, inValue:T) : T {
 		return untyped ioDestArray.__unsafe_set(inIndex,inValue);
 	}