QWindowsKeyMapper: make the code locale-independent

The C toupper function is locale-dependent. Given the right locale
(Türkiye, e.g.), toupper(i) is either

- İ (LATIN CAPITAL LETTER I WITH DOT ABOVE; if representable) or
- i (unchanged; if it isn't)

The latter is clearly wrong. The former might be what is wanted, but
since most locales these days are UTF-8, Í will be unlikely to be
representable in char.

So I conclude that what's intended here is that i gets mapped to I,
even in the Türkiye locale, so use the new QMiscUtils::toAsciiUpper()
instead of <ctype.h> toupper().

Fixes: QTBUG-109520
Change-Id: I6fee2fb15c2facae79f1727455180567698fed80
Reviewed-by: Samuel Ghinet <samuel.ghinet@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
(cherry picked from commit 7a6016aec4fdb446bd4f515fe7c08e1496cd2a7c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/plugins/platforms/windows/qwindowskeymapper.cpp

@@ -15,6 +15,7 @@
 #include <QtGui/qevent.h>
 #include <QtGui/private/qwindowsguieventdispatcher_p.h>
 #include <QtCore/private/qdebug_p.h>
+#include <QtCore/private/qtools_p.h>
 
 #if defined(WM_APPCOMMAND)
 #  ifndef FAPPCOMMAND_MOUSE
@@ -599,8 +600,7 @@ static inline quint32 toKeyOrUnicode(quint32 vk, quint32 scancode, unsigned char
 
 static inline int asciiToKeycode(char a, int state)
 {
-    if (a >= 'a' && a <= 'z')
-        a = toupper(a);
+    a = QtMiscUtils::toAsciiUpper(a);
     if ((state & Qt::ControlModifier) != 0) {
         if (a >= 0 && a <= 31)              // Ctrl+@..Ctrl+A..CTRL+Z..Ctrl+_
             a += '@';                       // to @..A..Z.._