[gtk/gbsneto/install-gtkpopovermenubar-h] build: Install gtkpopovermenubar.h

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit c82dcc8e3abb1edf2c2d7c5dbc96de79d152792b
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Sun Jun 9 15:40:55 2019 -0300

    build: Install gtkpopovermenubar.h
    
    It is not listed in 'gtk_public_headers', so it is not
    installed, and breaks anyone including gtk.h

 gtk/meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gtk/meson.build b/gtk/meson.build
index 98f80c4f04..c5bd9b154f 100644
--- a/gtk/meson.build
+++ b/gtk/meson.build
@@ -551,6 +551,7 @@ gtk_public_headers = files([
   'gtkpicture.h',
   'gtkpopover.h',
   'gtkpopovermenu.h',
+  'gtkpopovermenubar.h',
   'gtkprintcontext.h',
   'gtkprintoperation.h',
   'gtkprintoperationpreview.h',