[glom] Add missing explicit.

[Murray Cumming <murrayc src gnome org>]

commit a58ec1a70173c213a1ce5cfbfb03d5bf33476caf
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Oct 30 14:07:31 2015 +0100

    Add missing explicit.

 glom/libglom/connectionpool.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/glom/libglom/connectionpool.h b/glom/libglom/connectionpool.h
index 7233fe0..aab555b 100644
--- a/glom/libglom/connectionpool.h
+++ b/glom/libglom/connectionpool.h
@@ -57,7 +57,7 @@ class SharedConnection : public sigc::trackable
 {
 public:
   SharedConnection();
-  SharedConnection(const Glib::RefPtr<Gnome::Gda::Connection>& gda_connection);
+  explicit SharedConnection(const Glib::RefPtr<Gnome::Gda::Connection>& gda_connection);
   virtual ~SharedConnection();
 
   Glib::RefPtr<Gnome::Gda::Connection> get_gda_connection();