configure.ac: Don't link weston to cairo or image libraries

We were pulling in cairo and the image loading libraries through libshared.
Split out libshared into a core libshared and a libshared-cairo that
pulls in the extra libraries.

src/Makefile.am

@@ -126,7 +126,7 @@ if ENABLE_WAYLAND_COMPOSITOR
 wayland_backend = wayland-backend.la
 wayland_backend_la_LDFLAGS = -module -avoid-version
 wayland_backend_la_LIBADD = $(COMPOSITOR_LIBS) $(WAYLAND_COMPOSITOR_LIBS) \
-	../shared/libshared.la
+	../shared/libshared-cairo.la
 wayland_backend_la_CFLAGS =			\
 	$(COMPOSITOR_CFLAGS)			\
 	$(WAYLAND_COMPOSITOR_CFLAGS)		\

src/xwayland/Makefile.am

@@ -11,7 +11,7 @@ xwayland = xwayland.la
 xwayland_la_LDFLAGS = -module -avoid-version
 xwayland_la_LIBADD =			\
 	$(XWAYLAND_LIBS)		\
-	$(top_builddir)/shared/libshared.la
+	$(top_builddir)/shared/libshared-cairo.la
 xwayland_la_CFLAGS = $(GCC_CFLAGS) $(COMPOSITOR_CFLAGS)
 xwayland_la_SOURCES =				\
 	xwayland.h				\