Tools: Correctly show translated messages on more recent Visual Studio builds

Hi,

From issue #1169 (closed), it is known that on builds done by Visual Studio 2012 and later can cause the command-line tools in gio/ to show gibberish messages (or not shown at all) when showing translated messages, as it turns out that just using setlocale (LC_ALL, "") is not enough for the later Visual Studio CRTs for setting the default system locale.

This MR attempts to fix this by:

-SettingAdd a new macro in glibconfig.hglib-private.h for the appropriate string to pass into setlocale() to set the default system locale (".ACP" in this case).

-Use that macro in the tools in gio/.

This will make the translated messages show properly.

With blessings, thank you!