interface: Allows Delete key to kill processes

The delete key now can kill selected processes as Ctrl-K can while
the menu entry displaying the Ctrl+K shortcut remains. The purpose of
this is to allow convenience for those who are switching over from
gnome-system-monitor or other process managers which allow the
delete key to kill selected processes. This was accomplished by
adding an accelerator item with the delete key as the accelerator
and putting the menu entry of the KillProcess_Del on top of the
KillProcess menu entry so the latter shows over the former.

Issue mate-desktop#101

src/interface.cpp

@@ -66,6 +66,8 @@ static const GtkActionEntry menu_entries[] =
 
     { "EndProcess", NULL, N_("_End Process"), "<control>E",
       N_("Force process to finish normally"), G_CALLBACK (cb_end_process) },
+    { "KillProcess_Del", NULL, N_("_Kill Process"), "Delete",
+      N_("Force process to finish immediately"), G_CALLBACK (cb_kill_process) },
     { "KillProcess", NULL, N_("_Kill Process"), "<control>K",
       N_("Force process to finish immediately"), G_CALLBACK (cb_kill_process) },
     { "ChangePriority", NULL, N_("_Change Priority"), NULL,
@@ -137,6 +139,7 @@ static const char ui_info[] =
     "      <menuitem name=\"EditContProcessMenu\" action=\"ContProcess\" />"
     "      <separator />"
     "      <menuitem name=\"EditEndProcessMenu\" action=\"EndProcess\" />"
+    "      <menuitem name=\"EditKillProcessMenu\" action=\"KillProcess_Del\" />"
     "      <menuitem name=\"EditKillProcessMenu\" action=\"KillProcess\" />"
     "      <separator />"
     "      <menu name=\"EditChangePriorityMenu\" action=\"ChangePriority\" >"
@@ -175,6 +178,7 @@ static const char ui_info[] =
     "    <menuitem action=\"ContProcess\" />"
     "    <separator />"
     "    <menuitem action=\"EndProcess\" />"
+    "    <menuitem action=\"KillProcess_Del\" />"
     "    <menuitem action=\"KillProcess\" />"
     "    <separator />"
     "    <menu name=\"ChangePriorityMenu\" action=\"ChangePriority\" >"
@@ -780,6 +784,7 @@ update_sensitivity(ProcData *data)
     const char * const selected_actions[] = { "StopProcess",
                                               "ContProcess",
                                               "EndProcess",
+                                              "KillProcess_Del"
                                               "KillProcess",
                                               "ChangePriority",
                                               "MemoryMaps",