Ensure the use of C++20 standard for Poppler >= 24.04.

This resolves issue #96.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

tdefile-plugins/dependencies/poppler-tqt/ConfigureChecks.cmake

@@ -14,6 +14,8 @@ set( POPPLER_VERSION_PATCH ${CMAKE_MATCH_3} )
 math( EXPR POPPLER_VERSION_C "(${POPPLER_VERSION_MAJOR}*1000000) + (${POPPLER_VERSION_MINOR}*1000) + ${POPPLER_VERSION_PATCH}" )
 set( POPPLER_VERSION_C ${POPPLER_VERSION_C} CACHE INTERNAL "Poppler library version as code number" )
 
-if( NOT POPPLER_VERSION_C LESS 21012000 )
+if( NOT POPPLER_VERSION_C LESS 24004000 )
+  set( POPPLER_CXX_FEATURES cxx_std_20 CACHE INTERNAL "C++ standard required by Poppler" )
+elseif( NOT POPPLER_VERSION_C LESS 21012000 )
   set( POPPLER_CXX_FEATURES cxx_std_17 CACHE INTERNAL "C++ standard required by Poppler" )
 endif()