Revert using boost::locale to generate std::locales as boost::locale-
generated locales don't implement std::locale::facet and there was
a bug in the boost::locale ICU wrapper code that caused the wrong year
to be output for the last 3 days of December.
GCC's libstdc++ supports only the "C" locale on Windows and throws if
one attempts to create any other kind. For dates we work around this
by using wstrftime() to format according to locale and then convert
the UTF16 string to UTF8. wstrftime() interprets the time zone flags
%z, %Z, and %ZP differently so we process those first before calling
strftime. This will have the unfortunate effect of not localizing
timezone names but it's as close as we can get.
We can't use std::locale::global because all streams imbue it by
default and if it's not 'C' (aka std::locale::classic) then we
must imbue all the streams that we don't want localized, and that's
most of them.
Provides error checking for setting the C++ locale from the environment.
This is necessary both because the environment might have an invalid
locale, which would cause an unhandled exception crash.
On windows std::locale("") can't handle some Microsoft-style locale
strings (e.g. Spanish_Spain) so we use boost::locale's gen("") function
to set the locale--though even that can't handle a Microsoft-style
locale string with an appended charset (e.g. Spanish_Spain.1252) and
that's what glibc's setlocale(LC_ALL, NULL) emits.
