Use C locale for numbers in wx(File)Config.
Using the current locale decimal point in config files results in problems
when moving the files to another machine or even using a different locale on
the same one, so don't do it.
Always write the numbers using C locale and try to read them in C locale too
first, but also try the current locale if we failed for backwards
compatibility and to be tolerant with users who edit their config files by
hand.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64450
c3d73ce0-8a6f-49c7-b76d-
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