[glibmm] Created tag 2.52.0

[Murray Cumming <murrayc src gnome org>]

The unsigned tag '2.52.0' was created.

Tagger: Murray Cumming <murrayc murrayc com>
Date: Fri Jun 23 09:54:36 2017 +0200

    2.52.0

Changes since the last tag '2.51.7':

Daniel Boles (3):
      Variant: Use own get_n_children() instead of C API
      ActionMap: Revert accidental changes to Slot decls
      RefPtr: Clarify comment about undefined behaviour

Kjell Ahlstedt (1):
      Gio::UnixSocketAddress::create(): Remove a default value

Murray Cumming (1):
      2.52.0

Vyacheslav Yurkov (1):
      Gio::DBus::Proxy: Wrap call() and call_sync() methods. Bug 781818