As I said in 2ff121f2, passing a
POSIX-style locale name to the std::locale constructor on Windows is
decidedly odd, and apparently boost adds insult to injury by even
really attempting to use a UTF-8 one if that is what our code thinks
it wants. Or something.

This commit avoids the ton of
"warn:unotools.i18n:7996:3544:unotools/source/i18n/resmgr.cxx:123: CRT
Report Hook: ASSERT: f:\dd\vctools\crt\crtw32\stdcpp\xmbtowc.c(89) :
Assertion failed: ploc->_Mbcurmax == 1 || ploc->_Mbcurmax == 2" we
otherwise get when built with --enable-dbgutil and a current VS2015
(or 2017?).

Change-Id: I3a774dff7b12d9960f553c9f242e0463c6d13d5d
Reviewed-on: https://gerrit.libreoffice.org/54444Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Tor Lillqvist <tml@collabora.com>