Added missing include guards in a few headers

Considering the number of headers we have, it is a good idea to
avoid possible problems. For details, you may read:
  http://en.wikipedia.org/wiki/Include_guard

All headers should be ok now.

src/geomview.h

@@ -17,6 +17,9 @@
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#ifndef GEOMVIEW_H
+#define GEOMVIEW_H
+
 typedef struct W_GeometryView WGeometryView;
 
 
@@ -27,7 +30,4 @@ void WSetGeometryViewShownPosition(WGeometryView *gview, int x, int y);
 void WSetGeometryViewShownSize(WGeometryView *gview,
                                unsigned width, unsigned height);
 
-
-
-
-
+#endif  /* GEOMVIEW_H */

src/placement.h

@@ -20,6 +20,9 @@
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#ifndef PLACEMENT_H
+#define PLACEMENT_H
+
 void PlaceIcon(WScreen *scr, int *x_ret, int *y_ret, int head);
 
 /* Computes the intersecting length of two line sections */
@@ -32,3 +35,5 @@ void PlaceWindow(WWindow *wwin, int *x_ret, int *y_ret, unsigned width, unsigned
 
 /* Set the points x and y inside the screen */
 void get_right_position_on_screen(WScreen *scr, int *x, int *y, int size_x, int size_y);
+
+#endif  /* PLACEMENT_H */

src/shutdown.h

@@ -19,6 +19,9 @@
  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#ifndef SHUTDOWN_H
+#define SHUTDOWN_H
+
 /* shutdown modes */
 typedef enum {
     WSExitMode,
@@ -29,3 +32,5 @@ typedef enum {
 
 void Shutdown(WShutdownMode mode);
 void RestoreDesktop(WScreen *scr);
+
+#endif  /* SHUTDOWN_H */

util/wmmenugen.h

@@ -18,6 +18,9 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#ifndef WMMENUGEN_H
+#define WMMENUGEN_H
+
 #include <WINGs/WUtil.h>
 
 #include "../src/wconfig.h"
@@ -59,3 +62,4 @@ void parse_xdg(const char *file, void (*addWMMenuEntryCallback)(WMMenuEntry *aEn
 void parse_wmconfig(const char *file, void (*addWMMenuEntryCallback)(WMMenuEntry *aEntry));
 Bool wmconfig_validate_file(const char *filename, const struct stat *st, int tflags, struct FTW *ftw);
 
+#endif  /* WMMENUGEN_H */