[gnome-commander/ConvertWarningsToErrors] src/gnome-cmd-hintbox.cc: fix for -Wimplicit-fallthrough

[Uwe Scholz <uwescholz src gnome org>]

commit bc60ac14ba10912e3ba32a5183020f018e08a3c7
Author: Mamoru TASAKA <mtasaka fedoraproject org>
Date:   Mon Apr 24 12:54:39 2017 +0900

    src/gnome-cmd-hintbox.cc: fix for -Wimplicit-fallthrough
    
    ../src/gnome-cmd-hintbox.cc: In function 'void gnome_cmd_label_set_attributes(GtkLabel*, ...)':
    /usr/include/glib-2.0/glib/gmessages.h:334:31: error: this statement may fall through 
[-Werror=implicit-fallthrough=]
    
    src/gnome-cmd-hintbox.cc:336:11: note: in expansion of macro 'g_warning'
               g_warning ("%s: invalid PangoAttribute type %d",
               ^~~~~~~~~
    src/gnome-cmd-hintbox.cc:338:9: note: here
             case PANGO_ATTR_INVALID:
             ^~~~

 src/gnome-cmd-hintbox.cc |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/gnome-cmd-hintbox.cc b/src/gnome-cmd-hintbox.cc
index d7a103f..b9b5d77 100644
--- a/src/gnome-cmd-hintbox.cc
+++ b/src/gnome-cmd-hintbox.cc
@@ -335,6 +335,9 @@ gnome_cmd_label_set_attributes (GtkLabel *label, ...)
         default:
           g_warning ("%s: invalid PangoAttribute type %d",
                      G_STRFUNC, attr_type);
+#if defined (__GNUC__) && __GNUC__ >= 7
+          __attribute__ ((fallthrough));
+#endif
         case PANGO_ATTR_INVALID:
           attr = NULL;
           break;