[glibmm] Examples: Avoid a warning about unused code.

[Murray Cumming <murrayc src gnome org>]

commit 205bd350a538da7497de45b0cacf669e25dffcfd
Author: Murray Cumming <murrayc murrayc com>
Date:   Sat Nov 5 16:43:05 2016 +0100

    Examples: Avoid a warning about unused code.
    
    This useful warning seems to be new in g++ 6:
    
    thread/dispatcher2.cc:88:1: error: ‘{anonymous}::ThreadTimer::~ThreadTimer()’ defined but not used 
[-Werror=unused-function]
     ThreadTimer::~ThreadTimer()

 examples/thread/dispatcher2.cc |    4 ----
 1 files changed, 0 insertions(+), 4 deletions(-)
---
diff --git a/examples/thread/dispatcher2.cc b/examples/thread/dispatcher2.cc
index d56c5e7..9801161 100644
--- a/examples/thread/dispatcher2.cc
+++ b/examples/thread/dispatcher2.cc
@@ -85,10 +85,6 @@ ThreadTimer::ThreadTimer()
   signal_increment_.connect(sigc::mem_fun(*this, &ThreadTimer::timer_increment));
 }
 
-ThreadTimer::~ThreadTimer()
-{
-}
-
 void
 ThreadTimer::launch()
 {