added include for <optional> in G++17

[cheetahdotcat]

To fix an Error Message i was getting while compiling this in an Ubuntu Jammy container running on Balena OS (x86_64)

Consolidate compiler generated dependencies of target kvak
[  5%] Building CXX object CMakeFiles/kvak.dir/main.cpp.o
[ 11%] Building CXX object CMakeFiles/kvak.dir/costas.cpp.o
[ 17%] Building CXX object CMakeFiles/kvak.dir/demodulator.cpp.o
In file included from /app/kvak/demodulator.cpp:6:
/app/kvak/log.hpp:59:22: error: ‘optional’ in namespace ‘std’ does not name a template type
   59 |                 std::optional<std::reference_wrapper<std::ostream>> stream;
      |                      ^~~~~~~~
/app/kvak/log.hpp:8:1: note: ‘std::optional’ is defined in header ‘<optional>’; did you forget to ‘#include <optional>’?
    7 | #include <string.h>
  +++ |+#include <optional>
    8 | 
/app/kvak/log.hpp:85:14: error: ‘optional’ in namespace ‘std’ does not name a template type
   85 |         std::optional<std::reference_wrapper<std::ostream>> stream;
      |              ^~~~~~~~
/app/kvak/log.hpp:85:9: note: ‘std::optional’ is defined in header ‘<optional>’; did you forget to ‘#include <optional>’?
   85 |         std::optional<std::reference_wrapper<std::ostream>> stream;
      |         ^~~
/app/kvak/log.hpp: In constructor ‘kvak::log::log_wrapper::log_wrapper(const string&, std::ostream&)’:
/app/kvak/log.hpp:26:17: error: class ‘kvak::log::log_wrapper’ does not have any field named ‘stream’
   26 |                 stream(stream)
      |                 ^~~~~~
/app/kvak/log.hpp: In constructor ‘kvak::log::log_wrapper::log_ender::log_ender(std::ostream&)’:
/app/kvak/log.hpp:38:25: error: class ‘kvak::log::log_wrapper::log_ender’ does not have any field named ‘stream’
   38 |                         stream(stream)
      |                         ^~~~~~
/app/kvak/log.hpp: In destructor ‘kvak::log::log_wrapper::log_ender::~log_ender()’:
/app/kvak/log.hpp:44:35: error: ‘class kvak::log::log_wrapper::log_ender’ has no member named ‘stream’
   44 |                         if (this->stream) {
      |                                   ^~~~~~
/app/kvak/log.hpp:45:39: error: ‘class kvak::log::log_wrapper::log_ender’ has no member named ‘stream’
   45 |                                 this->stream.value().get() << "\x1b[0m" << std::endl;
      |                                       ^~~~~~
/app/kvak/log.hpp: In member function ‘kvak::log::log_wrapper::log_ender& kvak::log::log_wrapper::log_ender::operator<<(T&&)’:
/app/kvak/log.hpp:52:35: error: ‘class kvak::log::log_wrapper::log_ender’ has no member named ‘stream’
   52 |                         if (this->stream) {
      |                                   ^~~~~~
/app/kvak/log.hpp:53:39: error: ‘class kvak::log::log_wrapper::log_ender’ has no member named ‘stream’
   53 |                                 this->stream.value().get() << val;
      |                                       ^~~~~~
/app/kvak/log.hpp: In member function ‘void kvak::log::log_wrapper::mute()’:
/app/kvak/log.hpp:64:23: error: ‘class kvak::log::log_wrapper’ has no member named ‘stream’
   64 |                 this->stream.reset();
      |                       ^~~~~~
/app/kvak/log.hpp: In member function ‘void kvak::log::log_wrapper::redirect(std::ostream&)’:
/app/kvak/log.hpp:69:23: error: ‘class kvak::log::log_wrapper’ has no member named ‘stream’
   69 |                 this->stream = stream;
      |                       ^~~~~~
/app/kvak/log.hpp: In member function ‘kvak::log::log_wrapper::log_ender kvak::log::log_wrapper::operator<<(T&&)’:
/app/kvak/log.hpp:76:28: error: ‘class kvak::log::log_wrapper’ has no member named ‘stream’
   76 |                 if (!this->stream) {
      |                            ^~~~~~
/app/kvak/log.hpp:79:40: error: ‘class kvak::log::log_wrapper’ has no member named ‘stream’
   79 |                 return log_ender(this->stream.value().get() << this->prefix << val);
      |                                        ^~~~~~
make[2]: *** [CMakeFiles/kvak.dir/build.make:115: CMakeFiles/kvak.dir/demodulator.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:85: CMakeFiles/kvak.dir/all] Error 2
make: *** [Makefile:136: all] Error 2

[ikarus23]

Thanks for the fix. For me there was still an #include <array> missing in resample.cpp, causing

kvak/resample.cpp: In function ‘int main(int, char**)’:
kvak/resample.cpp:29:51: error: aggregate ‘std::array<std::complex<float>, 8192> data’ has incomplete type and cannot be defined
   29 |         std::array<std::complex<float>, 1024 * 8> data;
      |                                                   ^~~~