Check for decimal separator inconsistency in wxLocale::GetInfo().

Check for decimal separator inconsistency in wxLocale::GetInfo().

Under wxMSW it's possible to have mismatch between the CRT locale (used by
various printf-related functions) and the system locale (queried by
wxLocale::GetInfo()).

Warn if such a mismatch occurs and tell people to use wxLocale instead of just
setlocale() to change the locale.

See #12970.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68861 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775