[gtkmm] gtk-demo/demowindow: Use size_t to index in arrays

[Daniel Boles <dboles src gnome org>]

commit 343b64dcaf6857cc98b3abe5f9e88f761f8264a2
Author: Daniel Boles <dboles src gnome org>
Date:   Fri May 26 16:43:59 2017 +0100

    gtk-demo/demowindow: Use size_t to index in arrays
    
    int or unsigned int are not guaranteed to be wide enough. Of course,
    that will not matter in many practical cases, but it is better style to
    always use std::size_t when the purpose is to index into an array.

 demos/gtk-demo/demowindow.cc |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/demos/gtk-demo/demowindow.cc b/demos/gtk-demo/demowindow.cc
index 33d62dc..39bf983 100644
--- a/demos/gtk-demo/demowindow.cc
+++ b/demos/gtk-demo/demowindow.cc
@@ -29,6 +29,7 @@
 #include "demos.h"
 #include <iostream>
 #include <cstring>
+#include <cstddef>
 
 using std::isspace;
 using std::strlen;
@@ -257,7 +258,7 @@ void DemoWindow::load_file(const std::string& filename)
     int state = 0;
     bool in_para = false;
     auto start = refBufferInfo->get_iter_at_offset(0);
-    for (int i = 0; lines[i] != NULL; i++)
+    for (std::size_t i = 0; lines[i] != NULL; i++)
     {
       /* Make sure \r is stripped at the end for the poor windows people */
       lines[i] = g_strchomp(lines[i]);
@@ -382,7 +383,7 @@ void DemoWindow::add_data_tabs(const std::string& filename)
   {
     // Ignore this exception. It's no error, if resource_dir does not exist.
   }
-  for (unsigned int i = 0; i < resources.size(); ++i)
+  for (std::size_t i = 0; i < resources.size(); ++i)
   {
     const auto resource_name = resource_dir + "/" + resources[i];
     Gtk::Widget* widget = nullptr;