Use abbr_day_name to get the first letter of the day name (#9839).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@10202 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/views/gantts/show.html.erb

@@ -146,7 +146,7 @@ if show_days
   width =  zoom - 1
   %>
   <div style="left:<%= left %>px;top:37px;width:<%= width %>px;height:<%= height %>px;font-size:0.7em;<%= "background:#f1f1f1;" if wday > 5 %>" class="gantt_hdr">
-  <%= day_name(wday).first %>
+  <%= day_letter(wday) %>
   </div>
   <%
   left = left + width + 1