[libsigc++2] signal_impl: =delete copy and move operations.

[Murray Cumming <murrayc src gnome org>]

commit d14750e547387ab245af2d489c396fa699ab4263
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Nov 6 09:32:57 2015 +0100

    signal_impl: =delete copy and move operations.
    
    Prevent, copy and move constructors and assignment operators from
    being generated automatically. These are never used, but this
    will make sure of that.
    See https://bugzilla.gnome.org/show_bug.cgi?id=756484#c5

 sigc++/signal_base.h |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/sigc++/signal_base.h b/sigc++/signal_base.h
index d80fd2d..1842b02 100644
--- a/sigc++/signal_base.h
+++ b/sigc++/signal_base.h
@@ -51,6 +51,12 @@ struct SIGC_API signal_impl
 
   signal_impl();
 
+  signal_impl(const signal_impl& src) = delete;
+  signal_impl& operator=(const signal_impl& src) = delete;
+
+  signal_impl(signal_impl&& src) = delete;
+  signal_impl& operator=(signal_impl&& src) = delete;
+
   // only MSVC needs this to guarantee that all new/delete are executed from the DLL module
 #ifdef SIGC_NEW_DELETE_IN_LIBRARY_ONLY
   void* operator new(size_t size_);