Switch to C++23 (#432)

The standard became effective in October 2024:
https://isocpp.org/std/the-standard

Author: aobolensk

cmake/configure.cmake

@@ -25,7 +25,7 @@ set( CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin" )
 if ( MSVC AND (CMAKE_C_COMPILER_ID STREQUAL "Clang") AND (CMAKE_CXX_COMPILER_ID STREQUAL "Clang"))
     set( CMAKE_CXX_STANDARD 17 )
 else ()
-    set( CMAKE_CXX_STANDARD 20 )
+    set( CMAKE_CXX_STANDARD 23 )
 endif ()
 
 set(CMAKE_COMPILE_WARNING_AS_ERROR ON)