Resolves: tdf#158332 'fake' keystroke exits presentation

the fake keystroke is to make tooltips go away before menus which
used to be a problem versions of gtk3 < 3.24 that resultsed in no
menus appearing. Our min is still 3.18 so technically we need to retain
that until bumping past that as baseline.

Change-Id: I94aa309665c50c8ca310285d1e691030f443934a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/161081
Tested-by: Jenkins
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
diff --git a/sd/source/ui/slideshow/showwin.cxx b/sd/source/ui/slideshow/showwin.cxx
index 4bc0d41..d6ecc19 100644
--- a/sd/source/ui/slideshow/showwin.cxx
+++ b/sd/source/ui/slideshow/showwin.cxx
@@ -98,6 +98,12 @@ void ShowWindow::dispose()

void ShowWindow::KeyInput(const KeyEvent& rKEvt)
{
    // Ignore workaround of https://gitlab.gnome.org/GNOME/gtk/issues/1785
    // See calls to GtkSalFrame::makeFakeKeyPress (Fixed in GTK 3.24)
    bool bFakeKeyPress = rKEvt.GetKeyCode().GetFullCode() == 0;
    if (bFakeKeyPress)
        return;

    bool bReturn = false;

    if( SHOWWINDOWMODE_PREVIEW == meShowWindowMode )
@@ -127,11 +133,7 @@ void ShowWindow::KeyInput(const KeyEvent& rKEvt)
    }
    else if( SHOWWINDOWMODE_BLANK == meShowWindowMode )
    {
        bool bFakeKeyPress = rKEvt.GetKeyCode().GetFullCode() == 0;
        // Ignore workaround of https://gitlab.gnome.org/GNOME/gtk/issues/1785
        // See calls to GtkSalFrame::makeFakeKeyPress (Fixed in GTK 2.34)
        if (!bFakeKeyPress)
            RestartShow();
        RestartShow();
        bReturn = true;
    }
    else if( SHOWWINDOWMODE_PAUSE == meShowWindowMode )