compositor-wayland: Add a --sprawl option

This forces weston to create one output for every parent output.  This is
enabled by default if it detects a wl_fullscreen_shell.  The --sprawl
option is primarily to enable this on wl_shell.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
diff --git a/src/compositor.c b/src/compositor.c
index 5405faa..6b90bd8 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -4036,6 +4036,7 @@
 		"  --fullscreen\t\tRun in fullscreen mode\n"
 		"  --use-pixman\t\tUse the pixman (CPU) renderer\n"
 		"  --output-count=COUNT\tCreate multiple outputs\n"
+		"  --sprawl\t\tCreate one fullscreen output for every parent output\n"
 		"  --display=DISPLAY\tWayland display to connect to\n\n");
 
 #if defined(BUILD_RPI_COMPOSITOR) && defined(HAVE_BCM_HOST)