[glibmm] Remove Glib::unconst()

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 52fd4750b84b730c17b1d4a5cac20909cfbc48a1
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Mon Mar 13 15:18:20 2017 +0100

    Remove Glib::unconst()
    
    It's not used by glibmm or gtkmm. It's unnecessary.
    Use const_cast<>() directly instead.

 glib/glibmm/utility.h |   11 -----------
 1 files changed, 0 insertions(+), 11 deletions(-)
---
diff --git a/glib/glibmm/utility.h b/glib/glibmm/utility.h
index 3cbca14..5e17183 100644
--- a/glib/glibmm/utility.h
+++ b/glib/glibmm/utility.h
@@ -42,17 +42,6 @@ make_unique_ptr_gfree(T* p)
   return std::unique_ptr<T[], decltype(&g_free)>(p, &g_free);
 }
 
-// TODO: Deprecate this? We don't use it ourselves.
-/** Removes the const nature of a ptr
- *
- */
-template <class T>
-inline T*
-unconst(const T* t)
-{
-  return const_cast<T*>(t);
-}
-
 // Convert const gchar* to ustring, while treating NULL as empty string.
 inline Glib::ustring
 convert_const_gchar_ptr_to_ustring(const char* str)