Split the modules and include files between weston and libweston

The backends are now installed in lib/libweston-0, and the include
files that will be used by libweston in include/libweston-0. The other
modules and weston-specific include files are kept in the old paths.
A new wet_load_module() is added to load plugins in the old path,
which is not part of libweston, but weston only and defined in main.c.
To allow that to be used by out of tree weston plugins, the function
is declared in a new weston.h, installed in include/weston.

The -0 in the paths is the abi version of libweston, and it will also
be used by the libweston .so. If the abi changes the number will need
to be increased.

Signed-off-by: Giulio Camuffo <giuliocamuffo@gmail.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/Makefile.am b/Makefile.am
index fd10c13..92b4e5e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -5,6 +5,8 @@
 libexec_PROGRAMS =
 moduledir = $(libdir)/weston
 module_LTLIBRARIES =
+libweston_moduledir = $(libdir)/libweston-${LIBWESTON_ABI_VERSION}
+libweston_module_LTLIBRARIES =
 noinst_LTLIBRARIES =
 BUILT_SOURCES =
 
@@ -50,6 +52,7 @@
 	-I$(top_builddir)/protocol		\
 	-DDATADIR='"$(datadir)"'		\
 	-DMODULEDIR='"$(moduledir)"'		\
+	-DLIBWESTON_MODULEDIR='"$(libweston_moduledir)"' \
 	-DLIBEXECDIR='"$(libexecdir)"'		\
 	-DBINDIR='"$(bindir)"'
 
@@ -212,8 +215,8 @@
 wayland_sessiondir = $(datadir)/wayland-sessions
 dist_wayland_session_DATA = src/weston.desktop
 
-westonincludedir = $(includedir)/weston
-westoninclude_HEADERS =				\
+libwestonincludedir = $(includedir)/libweston-${LIBWESTON_ABI_VERSION}
+libwestoninclude_HEADERS =				\
 	src/version.h				\
 	src/compositor.h			\
 	src/compositor-drm.h			\
@@ -223,19 +226,21 @@
 	src/compositor-wayland.h		\
 	src/compositor-x11.h			\
 	src/timeline-object.h			\
-	src/weston.h				\
 	shared/matrix.h				\
 	shared/config-parser.h			\
 	shared/zalloc.h				\
 	shared/platform.h
 
+westonincludedir = $(includedir)/weston
+westoninclude_HEADERS = src/weston.h
+
 if ENABLE_IVI_SHELL
 westoninclude_HEADERS +=				\
 	ivi-shell/ivi-layout-export.h
 endif
 
 if ENABLE_EGL
-module_LTLIBRARIES += gl-renderer.la
+libweston_module_LTLIBRARIES += gl-renderer.la
 gl_renderer_la_LDFLAGS = -module -avoid-version
 gl_renderer_la_LIBADD = $(COMPOSITOR_LIBS) $(EGL_LIBS)
 gl_renderer_la_CFLAGS =				\
@@ -252,7 +257,7 @@
 endif
 
 if ENABLE_X11_COMPOSITOR
-module_LTLIBRARIES += x11-backend.la
+libweston_module_LTLIBRARIES += x11-backend.la
 x11_backend_la_LDFLAGS = -module -avoid-version
 x11_backend_la_LIBADD = $(COMPOSITOR_LIBS) $(X11_COMPOSITOR_LIBS) \
 	libshared-cairo.la
@@ -278,7 +283,7 @@
 	shared/helpers.h
 
 if ENABLE_DRM_COMPOSITOR
-module_LTLIBRARIES += drm-backend.la
+libweston_module_LTLIBRARIES += drm-backend.la
 drm_backend_la_LDFLAGS = -module -avoid-version
 drm_backend_la_LIBADD =				\
 	$(COMPOSITOR_LIBS)			\
@@ -309,7 +314,7 @@
 endif
 
 if ENABLE_WAYLAND_COMPOSITOR
-module_LTLIBRARIES += wayland-backend.la
+libweston_module_LTLIBRARIES += wayland-backend.la
 wayland_backend_la_LDFLAGS = -module -avoid-version
 wayland_backend_la_LIBADD =			\
 	$(COMPOSITOR_LIBS)			\
@@ -332,7 +337,7 @@
 endif
 
 if ENABLE_HEADLESS_COMPOSITOR
-module_LTLIBRARIES += headless-backend.la
+libweston_module_LTLIBRARIES += headless-backend.la
 headless_backend_la_LDFLAGS = -module -avoid-version
 headless_backend_la_LIBADD = $(COMPOSITOR_LIBS) libshared.la
 headless_backend_la_CFLAGS = $(COMPOSITOR_CFLAGS) $(AM_CFLAGS)
@@ -343,7 +348,7 @@
 endif
 
 if ENABLE_FBDEV_COMPOSITOR
-module_LTLIBRARIES += fbdev-backend.la
+libweston_module_LTLIBRARIES += fbdev-backend.la
 fbdev_backend_la_LDFLAGS = -module -avoid-version
 fbdev_backend_la_LIBADD =			\
 	$(COMPOSITOR_LIBS)			\
@@ -365,7 +370,7 @@
 endif
 
 if ENABLE_RDP_COMPOSITOR
-module_LTLIBRARIES += rdp-backend.la
+libweston_module_LTLIBRARIES += rdp-backend.la
 rdp_backend_la_LDFLAGS = -module -avoid-version
 rdp_backend_la_LIBADD = $(COMPOSITOR_LIBS) \
 	$(RDP_COMPOSITOR_LIBS) \