[gtkmm] example_glarea.cc: Fix Build on Visual Studio 2013

[Chun-wei Fan <fanchunwei src gnome org>]

commit 1ee68b62ce9df596cf3bf6f10dc469c1be489966
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Thu Sep 17 15:59:21 2015 +0800

    example_glarea.cc: Fix Build on Visual Studio 2013
    
    Apparently there is another quirk in Visual Studio 2013's C++
    support, so one must use std::vector to declare the class member, and
    then use a member initializer list to initialize it properly by the
    constructor, if not doing it one-by-one in the constructor itself.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=754863

 demos/gtk-demo/example_glarea.cc |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/demos/gtk-demo/example_glarea.cc b/demos/gtk-demo/example_glarea.cc
index 59a7808..4baf3ff 100644
--- a/demos/gtk-demo/example_glarea.cc
+++ b/demos/gtk-demo/example_glarea.cc
@@ -6,6 +6,7 @@
 
 #include <iostream>
 #include <string>
+#include <vector>
 
 #include <gtkmm.h>
 #include <giomm/resource.h>
@@ -46,7 +47,7 @@ protected:
   GLuint m_Program {0};
   GLuint m_Mvp {0};
 
-  float m_RotationAngles[N_AXIS] {0.0f, 0.0f, 0.0f};
+  std::vector<float> m_RotationAngles;
 
   void on_axis_value_change(int axis, const Glib::RefPtr<Gtk::Adjustment>& adj);
 
@@ -65,7 +66,7 @@ Gtk::Window* do_glarea()
   return new Example_GLArea();
 }
 
-Example_GLArea::Example_GLArea()
+Example_GLArea::Example_GLArea() : m_RotationAngles(N_AXIS, 0.0f)
 {
   set_title("GL Area");
   set_default_size(400, 600);