Use the recommended name-based NLS API rather than legacy functions
taking LCID.
Preserve compatibility with Windows XP by keeping the old code for now,
but it will be removed after 3.2.0.
This is tidier than using #ifdefs in the same common file and also
ensures that initializing wxLocale affects wxUILocale too, which will be
important for compatibility when the code elsewhere is modified to use
wxUILocale::GetInfo() instead of wxLocale::GetInfo() in the upcoming
commits.
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