ivi-shell: add include guards on ivi-shell.h

It's our standard practice. This file will get used a bit more in the
future.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>

ivi-shell/ivi-shell.h

@@ -23,6 +23,9 @@
  * SOFTWARE.
  */
 
+#ifndef WESTON_IVI_SHELL_H
+#define WESTON_IVI_SHELL_H
+
 #include <stdbool.h>
 
 #include "compositor.h"
@@ -65,3 +68,5 @@ input_panel_setup(struct ivi_shell *shell);
 
 void
 input_panel_destroy(struct ivi_shell *shell);
+
+#endif /* WESTON_IVI_SHELL_H */