convertFromString<double>() does not restore the old locale properly

[unvestigate]

I have found that convertFromString() in basic_types.cpp sometimes sets an incorrect locale after converting the string to a double. The old_locale string starts out getting the value "C", which in my case is correct. However, after the next call to setlocale(), which sets it to "C" (ie. the same locale) the old_locale string is garbage.

Changing old_locale to "std::string" instead of "const auto", ie. making a local copy, fixes the error. This is tested on windows with both MSVC 2015 and 2019.

[facontidavide]

fixed. thanks a lot