Merge pull request #9434 from alalek:fix_numpy_warning

modules/python/common.cmake

@@ -118,6 +118,7 @@ if(MSVC AND NOT ENABLE_NOISY_WARNINGS)
 endif()
 
 ocv_warnings_disable(CMAKE_CXX_FLAGS -Woverloaded-virtual -Wunused-private-field)
+ocv_warnings_disable(CMAKE_CXX_FLAGS -Wundef) # accurate guard via #pragma doesn't work (C++ preprocessor doesn't handle #pragma)
 
 if(MSVC AND NOT BUILD_SHARED_LIBS)
   set_target_properties(${the_module} PROPERTIES LINK_FLAGS "/NODEFAULTLIB:atlthunk.lib /NODEFAULTLIB:atlsd.lib /DEBUG")