Gaudi v33r1 build fails with Mircosoft GSL 3.0.1 and clang10

Dear Gaudi developers,

Following Ben's requiest we have updated GSL to 3.0.1 in LCG nightlies and now clang10 builds fail for Gaudi v33r1 in two places, see below.

Could you please have a look?

Kind Regards, Dmitri

  gsl::span args{argv, argc}
                       ^~~~
/workspace/build/frameworks/Gaudi-v33r1/src/Gaudi/v33r1/GaudiKernel/src/Lib/GaudiMain.cpp:27:24: note: insert an explicit cast to silence this issue
  gsl::span args{argv, argc}
                       ^~~~
                       static_cast<size_type>( )
1 error generated.
make[5]: *** [GaudiKernel/CMakeFiles/GaudiKernel.dir/src/Lib/GaudiMain.cpp.o] Error 1```

and 

```/workspace/build/frameworks/Gaudi-v33r1/src/Gaudi/v33r1/GaudiKernel/src/Lib/Application.cpp:118:48: error: non-constant-expression cannot be narrowed from type 'long' to 'gsl::span::size_type' (aka 'unsigned long') in initializer list [-Wc++11-narrowing]
  gsl::span                   py_opts{options, n}
                                               ^
/workspace/build/frameworks/Gaudi-v33r1/src/Gaudi/v33r1/GaudiKernel/src/Lib/Application.cpp:118:48: note: insert an explicit cast to silence this issue
  gsl::span                   py_opts{options, n}
                                               ^
                                               static_cast<size_type>( )
1 error generated.
make[5]: *** [GaudiKernel/CMakeFiles/GaudiKernel.dir/src/Lib/Application.cpp.o] Error 1```