Made the lib work with -fno-exceptions (at least for now).

source/mijin/io/stream.hpp

@@ -457,6 +457,7 @@ inline const char* errorName(StreamError error) MIJIN_NOEXCEPT
     return "<invalid error>";
 }
 
+#if MIJIN_ENABLE_EXCEPTIONS // these functions don't make sense with exceptions disabled
 inline void throwOnError(mijin::StreamError error)
 {
     if (error == mijin::StreamError::SUCCESS) {
@@ -500,6 +501,7 @@ inline decltype(auto) throwOnError(StreamResult<TSuccess>&& result, const std::s
     }
     return *result;
 }
+#endif // MIJIN_ENABLE_EXCEPTIONS
 } // namespace mijin
 
 #endif // !defined(MIJIN_IO_STREAM_HPP_INCLUDED)