[glibmm] BalancedTree: Make a constructor explicit.

[Murray Cumming <murrayc src gnome org>]

commit 5e1888bc1a7a3c9eddd88dd7ce9a33e0ad87e33f
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon Dec 12 10:37:45 2016 +0100

    BalancedTree: Make a constructor explicit.

 glib/src/balancedtree.hg |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/glib/src/balancedtree.hg b/glib/src/balancedtree.hg
index 5444046..a7628fc 100644
--- a/glib/src/balancedtree.hg
+++ b/glib/src/balancedtree.hg
@@ -67,7 +67,7 @@ protected:
     gobject_ = g_tree_new_full(on_compare_tree, &key_compare_slot, on_destroy_key, on_destroy_value);
   }
 
-  BalancedTree(const CompareFunc &key_compare_slot_) :
+  explicit BalancedTree(const CompareFunc &key_compare_slot_) :
     key_compare_slot(key_compare_slot_)
   {
     gobject_ = g_tree_new_full(on_compare_tree, &key_compare_slot, on_destroy_key, on_destroy_value);