File fix-build.patch of Package kvak

diff --git a/demodulator.hpp b/demodulator.hpp
index 65fbecc..762ca80 100644
--- a/demodulator.hpp
+++ b/demodulator.hpp
@@ -9,6 +9,7 @@
 #include <deque>
 #include <memory>
 #include <vector>
+#include <optional>
 
 #include "costas.hpp"
 #include "gardner.hpp"
diff --git a/log.hpp b/log.hpp
index 77fa8f2..72ec7ee 100644
--- a/log.hpp
+++ b/log.hpp
@@ -5,6 +5,7 @@
 #include <string>
 #include <ostream>
 #include <string.h>
+#include <optional>
 
 namespace kvak::log {