qt: Expect UTF-8 on stderr on Windows

* lang/qt/src/threadedjobmixin.cpp (stringFromGpgOutput): Expect
UTF-8.

--
In recent versions more and more output was changed to be
UTF-8 on Windows. Werner advised to always expect UTF-8
diagnostics.

lang/qt/src/threadedjobmixin.cpp

@@ -53,53 +53,10 @@
 using namespace QGpgME;
 using namespace GpgME;
 
-#ifdef Q_OS_WIN
-#include <windows.h>
-
-static QString fromEncoding (unsigned int src_encoding, const char *data)
-{
-    int n = MultiByteToWideChar(src_encoding, 0, data, -1, NULL, 0);
-    if (n < 0) {
-        return QString();
-    }
-
-    wchar_t *result = (wchar_t *) malloc ((n+1) * sizeof *result);
-
-    n = MultiByteToWideChar(src_encoding, 0, data, -1, result, n);
-    if (n < 0) {
-        free(result);
-        return QString();
-    }
-    const auto ret = QString::fromWCharArray(result, n);
-    free(result);
-    return ret;
-}
-#endif
-
 static QString stringFromGpgOutput(const QByteArray &ba)
 {
 #ifdef Q_OS_WIN
-    /* Qt on Windows uses GetACP while GnuPG prefers
+    return QString::fromUtf8(ba);
-     * GetConsoleOutputCP.
-     *
-     * As we are not a console application GetConsoleOutputCP
-     * usually returns 0.
-     * From experience the closest thing that let's us guess
-     * what GetConsoleOutputCP returns for a console application
-     * it appears to be the OEMCP.
-     */
-    unsigned int cpno = GetConsoleOutputCP ();
-    if (!cpno) {
-        cpno = GetOEMCP();
-    }
-    if (!cpno) {
-        cpno = GetACP();
-    }
-    if (!cpno) {
-        return QString();
-    }
-
-    return fromEncoding(cpno, ba.constData());
 #else
     return QString::fromLocal8Bit(ba);
 #endif