Make Int64.neg use negation on java and not bitwise negation.

std/java/_std/haxe/Int64.hx

@@ -111,7 +111,7 @@ import java.StdTypes.Int64 in NativeInt64;
 
 	public static inline function neg( a : Int64 ) : Int64
 	{
-		return (~(a.asNative())).ofNative();
+		return (-(a.asNative())).ofNative();
 	}
 
 	public static inline function isNeg( a : Int64 ) : Bool