Previously, we enforced code page 850 for all console input and output,
which breaks with non-western scripts. Since more recent Windows shells
are able to display Unicode properly, this patch now enforces UTF-8 and
falls back to code page 850 only if UTF-8 is unsupported.
Non-Windows systems default to UTF-8, but can override the codec
by setting the LANG environment variable to something other than C.
Resolves#3049.
QTextStream uses the system default locale, but this breaks in
various situations: (1) It does not work on the native Windows shell
(cmd.exe, Powershell), since the default Windows locale is Windows-1252,
but the shell uses Windows-850. (2) It also breaks on *nix systems where
the locale is Latin1 or C, which is the case for most CI systems or
build servers.
We allow overriding the detected codec by setting the ENCODING_OVERRIDE
environment variable, but otherwise prefer Windows-850 on Windows and
UTF-8 on any other system, even if LANG is set to something else.
This resolves#2413
