Disable the use of std::exception_ptr for MSVC 2010.

While <exception> does define this type in this version of the compiler, it's
non-conforming and doesn't define conversion to bool, so we can't test whether
it is valid or not.

We could work around it but for now just disable the use of exception_ptr with
VC10 and only use it for VC11+.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77483 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775