[LyX/master] Replace deprecated std::result_of, make nod library compatible with C++20

[Yuriy Skalko]

commit a2c126f867e12ae166c64fd625101c3c49ee2933
Author: Yuriy Skalko <yuriy.skalko at gmail.com>
Date:   Wed Dec 30 01:35:25 2020 +0200

    Replace deprecated std::result_of, make nod library compatible with C++20
---
 3rdparty/nod/nod.hpp |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/3rdparty/nod/nod.hpp b/3rdparty/nod/nod.hpp
index 5c4a93c..4cc18fe 100644
--- a/3rdparty/nod/nod.hpp
+++ b/3rdparty/nod/nod.hpp
@@ -269,7 +269,11 @@ namespace nod {
 	{
 		public:
 			/// Result type when calling the accumulating function operator.
+#if __cplusplus >= 201703L
+			using result_type = typename std::invoke_result<F, T, typename S::slot_type::result_type>::type;
+#else
 			using result_type = typename std::result_of<F(T, typename S::slot_type::result_type)>::type;
+#endif
 
 			/// Construct a signal_accumulator as a proxy to a given signal
 			//