Fix off-by-one error in QTranslatorPrivate::do_load()

The central loop starts by reading five bytes; but
the loop condition only checked that four were available.

Change-Id: I244cecacabeffbac10ad94081f32847f912d95d9
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: hjk <hjk@qt.io>

src/corelib/kernel/qtranslator.cpp

@@ -824,7 +824,7 @@ bool QTranslatorPrivate::do_load(const uchar *data, int len, const QString &dire
     data += MagicLength;
 
     QStringList dependencies;
-    while (data < end - 4) {
+    while (data < end - 5) {
         quint8 tag = read8(data++);
         quint32 blockLen = read32(data);
         data += 4;