New shutdown.h file

The new shutdown.h file includes the shutdown modes and the functions
to shutdown Window Maker.

The function definitios were moved from funcs.h and the struct WShutdownMode
from WindowMaker.h.

Now, externs are not needed, only include shutdown.h

src/shutdown.h

@@ -0,0 +1,31 @@
+/* shutdown.c - Shutdown functions
+ *
+ *  Window Maker window manager
+ *
+ *  Copyright (c) 2013 Window Maker Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/* shutdown modes */
+typedef enum {
+    WSExitMode,
+    WSLogoutMode,
+    WSKillMode,
+    WSRestartPreparationMode
+} WShutdownMode;
+
+void Shutdown(WShutdownMode mode);
+void RestoreDesktop(WScreen *scr);