Fix for Visual Studio 2019 v16.7.0
Fix for Visual Studio 2019 v16.7.0

Silly workaround for rootcling not being able to parse the STL headers anymore after the update of Visual Studio to the version 16.7.0:
```
  Generating G__Core.cxx, ../bin/libCore.rootmap
  In file included from input_line_5:1:
  In file included from C:/Users/sftnight/build/release/include\Rtypes.h:191:
  In file included from C:/Users/sftnight/build/release/include/TGenericClassInfo.h:21:
  In file included from C:/Users/sftnight/build/release/include/TSchemaHelper.h:17:
  In file included from C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.291  10\\include\string:11:
  In file included from C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.291  10\\include\xstring:14:
  In file included from C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.291  10\\include\xmemory:16:
  In file included from C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.291  10\\include\xutility:15:
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\utility(137,9): error G08EB1F86: expected member name or ';' after declaration specifiers [C:\Users\sftnight\build\release\core\G__Core.vcxproj]
          !_Is_implicitly_default_constructible<_Uty1>::value || !_Is_implicitly_default_constructible<_Uty2>::value)
          ^
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\utility(137,9): error GC66A3811: expected ')' [C:\Users\sftnight\build\release\core\G__Core.vcxproj]
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\utility:136:23: note: to match this '('
      constexpr explicit(
                        ^
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\utility(218,24): error G08EB1F86: expected member name or ';' after declaration specifiers [C:\Users\sftnight\build\release\core\G__Core.vcxproj]
      constexpr explicit(!is_convertible_v<const _Other1&, _Ty1> || !is_convertible_v<const _Other2&, _Ty2>)
      ~~~~~~~~~~~~~~~~~~ ^
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\utility(218,24): error GC66A3811: expected ')' [C:\Users\sftnight\build\release\core\G__Core.vcxproj]
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\utility:218:23: note: to match this '('
      constexpr explicit(!is_convertible_v<const _Other1&, _Ty1> || !is_convertible_v<const _Other2&, _Ty2>)
                        ^
  In file included from input_line_5:1:
  In file included from C:/Users/sftnight/build/release/include\Rtypes.h:191:
  In file included from C:/Users/sftnight/build/release/include/TGenericClassInfo.h:21:
  In file included from C:/Users/sftnight/build/release/include/TSchemaHelper.h:17:
  In file included from C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\string:11:
  In file included from C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\xstring:14:
  In file included from C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\xmemory:16:
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\xutility(63,31): error G959205E0: '_To' does not refer to a value [C:\Users\sftnight\build\release\core\G__Core.vcxproj]
      return __builtin_bit_cast(_To, _Val);
                                ^
  C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\\include\xutility:51:17: note: declared here
  template <class _To, class _From,
                  ^
CUSTOMBUILD : error : Error loading the default header files. [C:\Users\sftnight\build\release\core\G__Core.vcxproj]
```
To be checked/removed after the upgrade of LLVM & Clang

root-mirror/cling,root-mirror/cling,root-mirror/cling,root-mirror/cling,root-mirror/cling,root-mirror/cling