Don't use CUDA/DNN stuff in Visual Studio 2017.

dlib/cmake_utils/set_compiler_specific_options.cmake

@@ -14,6 +14,15 @@ elseif(MSVC AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 19.0.24215.1 )
    message(STATUS "Also, be aware that Visual Studio's version naming is confusing, in particular, there are multiple versions of 'update 3'")
    message(STATUS "So if you are getting this message you need to update to the newer version of Visual Studio to use full C++11.")
    set(USING_OLD_VISUAL_STUDIO_COMPILER 1)
+elseif(MSVC AND (MSVC_VERSION EQUAL 1911 OR MSVC_VERSION EQUAL 1910))
+   message(STATUS "******************************************************************************************")
+   message(STATUS "Visual Studio 2017 has incomplete C++11 support and is unable to compile the DNN examples.")
+   message(STATUS "So we are disabling the deep learning tools.  If you want to use the DNN tools in ")
+   message(STATUS "dlib then use Visual Studio 2015 which, surprisingly, has better C++11 support.")
+   message(STATUS "Or if you are reading this in the future and a newer version of Visual Studio that ")
+   message(STATUS "supports C++11 is available then use that.")
+   message(STATUS "******************************************************************************************")
+   set(USING_OLD_VISUAL_STUDIO_COMPILER 1)
 endif()
 
 if(CMAKE_COMPILER_IS_GNUCXX)