[LyX/master] Correct the method signature of MenuTranslator::translate for Qt5

[Stephan Witt]

commit 6cbaad9398a071e6db6c2b6e577877622a4d02e4
Author: Stephan Witt <sw...@lyx.org>
Date:   Sat Aug 23 16:01:03 2014 +0200

    Correct the method signature of MenuTranslator::translate for Qt5

diff --git a/src/frontends/qt4/GuiApplication.cpp 
b/src/frontends/qt4/GuiApplication.cpp
index f1c2e90..5ee0c58 100644
--- a/src/frontends/qt4/GuiApplication.cpp
+++ b/src/frontends/qt4/GuiApplication.cpp
@@ -632,9 +632,15 @@ public:
                : QTranslator(parent)
        {}
 
+#if QT_VERSION >= 0x050000
+       virtual QString translate(const char * /* context */,
+               const char *sourceText,
+               const char * /* disambiguation */ = 0, int /* n */ = -1) const
+#else
        QString translate(const char * /*context*/,
          const char * sourceText,
          const char * /*comment*/ = 0) const
+#endif
        {
                string const s = sourceText;
                if (s == N_("About %1") || s == N_("Preferences")