[gtksourceviewmm] Adapt dynamic casts for Glib::RefPtr as std::shared_ptr.

[Murray Cumming <murrayc src gnome org>]

commit fb11bb10c6341c90c498ce06ce88c76be8c60d49
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Apr 7 15:16:03 2017 +0200

    Adapt dynamic casts for Glib::RefPtr as std::shared_ptr.

 gtksourceview/src/view.ccg |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/gtksourceview/src/view.ccg b/gtksourceview/src/view.ccg
index 6a470cd..3449c9a 100644
--- a/gtksourceview/src/view.ccg
+++ b/gtksourceview/src/view.ccg
@@ -50,15 +50,15 @@ View::View(const Glib::RefPtr<Buffer> &a_buffer) :
 Glib::RefPtr<const Buffer>
 View::get_source_buffer () const
 {
-    Glib::RefPtr<const Gtk::TextBuffer> buffer = get_buffer();
-    return Glib::RefPtr<const Buffer>::cast_dynamic(buffer);
+    auto buffer = get_buffer();
+    return std::dynamic_pointer_cast<const Buffer>(buffer);
 }
 
 Glib::RefPtr<Buffer>
 View::get_source_buffer ()
 {
-    Glib::RefPtr<Gtk::TextBuffer> buffer = get_buffer();
-    return Glib::RefPtr<Buffer>::cast_dynamic(buffer);
+    auto buffer = get_buffer();
+    return std::dynamic_pointer_cast<Buffer>(buffer);
 }
 
 void