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/Makefile.am b/Makefile.am
index fe08d94..318a837 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -893,6 +893,7 @@
 ivi_shell_la_SOURCES =				\
 	ivi-shell/ivi-layout-export.h		\
 	ivi-shell/ivi-layout-private.h		\
+	ivi-shell/ivi-layout-shell.h		\
 	ivi-shell/ivi-layout.c			\
 	ivi-shell/ivi-layout-transition.c	\
 	ivi-shell/ivi-shell.h			\