gtk3: add some missing SolarMutexGuards (thanks to mst for noticing)

vcl/unx/gtk/a11y/atkwindow.cxx

@@ -30,6 +30,7 @@
 #include "precompiled_vcl.hxx"
 
 #include <unx/gtk/gtkframe.hxx>
+#include <vcl/svapp.hxx>
 #include <vcl/window.hxx>
 #include "vcl/popupmenuwindow.hxx"
 
@@ -131,6 +132,7 @@ init_from_window( AtkObject *accessible, Window *pWindow )
 static gint
 ooo_window_wrapper_clear_focus(gpointer)
 {
+    SolarMutexGuard aGuard;
     atk_focus_tracker_notify( NULL );
     return FALSE;
 }

vcl/unx/gtk/app/gtkdata.cxx

@@ -880,6 +880,7 @@ gboolean GtkData::userEventFn( gpointer data )
 extern "C" {
     static gboolean call_userEventFn( void *data )
     {
+        SolarMutexGuard aGuard;
         return GtkData::userEventFn( data );
     }
 }

vcl/unx/gtk/window/gtkframe.cxx

@@ -3219,6 +3219,8 @@ gboolean GtkSalFrame::signalFocus( GtkWidget*, GdkEventFocus* pEvent, gpointer f
 extern "C" {
 gboolean implDelayedFullScreenHdl (void *pWindow)
 {
+    SolarMutexGuard aGuard;
+
     /* #i110881# workaround a gtk issue (see
        https://bugzilla.redhat.com/show_bug.cgi?id=623191#c8)
        gtk_window_fullscreen can fail due to a race condition,