cppapi/server/idl: Ignore unused-parameter for clang as well

Exposed with the new C++11 compilation, but ultimately forgotten in
cc8f943 (cppapi/server: Ignore warnings for generated code,
2019-11-15).

Author: t-b

cppapi/server/idl/CMakeLists.txt

@@ -82,7 +82,7 @@ else(WIN32)
     if(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
       target_compile_options(idl_objects PRIVATE -Wno-maybe-uninitialized -Wno-unused-parameter)
     elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-      target_compile_options(idl_objects PRIVATE -Wno-sometimes-uninitialized -Wno-unused-variable)
+      target_compile_options(idl_objects PRIVATE -Wno-sometimes-uninitialized -Wno-unused-variable -Wno-unused-parameter)
     endif()
 
     install(FILES ${CMAKE_CURRENT_BINARY_DIR}/tango.h DESTINATION "${CMAKE_INSTALL_FULL_INCLUDEDIR}/tango/idl")