ivi-shell: introduce ivi-layout-shell.h

This new header encapsulates the API that ivi-layout offers to
ivi-shell.c to call.

ivi-shell.c no longer uses ivi-layout-private.h. This limits the
ivi-layout internal structures to just ivi-layout code.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Emre Ucan <eucan@de.adit-jv.com>
diff --git a/ivi-shell/ivi-shell.c b/ivi-shell/ivi-shell.c
index 7a53769..2ff3784 100644
--- a/ivi-shell/ivi-shell.c
+++ b/ivi-shell/ivi-shell.c
@@ -44,7 +44,7 @@
 #include "ivi-shell.h"
 #include "ivi-application-server-protocol.h"
 #include "ivi-layout-export.h"
-#include "ivi-layout-private.h"
+#include "ivi-layout-shell.h"
 #include "shared/helpers.h"
 
 /* Representation of ivi_surface protocol object. */