[Release][CMake] Convert macros to functions in DuneEnableAllPackages

All of the macros in DuneEnableAllPackage cause their side effects by
modifying properties, so there is no point in having them as macros,
which are more fragile than functions and pollute the outside variable
scope.

cmake/modules/DuneEnableAllPackages.cmake

@@ -86,7 +86,7 @@ function(dune_register_package_flags)
 endfunction(dune_register_package_flags)
 
 
-macro(dune_enable_all_packages)
+function(dune_enable_all_packages)
   include(CMakeParseArguments)
   set(OPTIONS APPEND VERBOSE)
   set(SINGLEARGS)
@@ -187,10 +187,10 @@ Update the cmake_minimum_required() call in your main CMakeLists.txt file to get
     message("Libraries for this project: ${all_libs}")
   endif(DUNE_ENABLE_ALL_PACKAGES_VERBOSE)
 
-endmacro(dune_enable_all_packages)
+endfunction(dune_enable_all_packages)
 
 
-macro(dune_library_add_sources lib)
+function(dune_library_add_sources lib)
 
   # This only works for CMAKE 3.1+ because target_sources() - which we use to add sources to the
   # libraries after creating them - was added in that version
@@ -221,4 +221,4 @@ List of libraries defined in dune_enable_all_packages: ${DUNE_ENABLE_ALL_PACKAGE
   foreach(source ${DUNE_LIBRARY_ADD_SOURCES_SOURCES})
     target_sources(${lib} PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/${source})
   endforeach()
-endmacro()
+endfunction()