[LyX/master] Add Qt-internal GUI string

[Juergen Spitzmueller]

commit 6d4a63d86b4460526857ab1c4fbeae5aba00e10e
Author: Juergen Spitzmueller <sp...@lyx.org>
Date:   Mon Dec 17 13:39:45 2018 +0100

    Add Qt-internal GUI string
---
 src/frontends/qt4/GuiApplication.cpp |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/src/frontends/qt4/GuiApplication.cpp 
b/src/frontends/qt4/GuiApplication.cpp
index b9ba830..3a5fd12 100644
--- a/src/frontends/qt4/GuiApplication.cpp
+++ b/src/frontends/qt4/GuiApplication.cpp
@@ -683,6 +683,7 @@ public:
                _("About %1");
                _("Preferences");
                _("Reconfigure");
+               _("Restore Defaults");
                _("Quit %1");
                _("&OK");
                // Already in po: "Cancel", "&Cancel"