Pass argc pointer to parse_options()

This lets us keep argc up to date as the backend picks out arguments
from the argv array.
diff --git a/src/compositor-fbdev.c b/src/compositor-fbdev.c
index 1df3bbc..070d187 100644
--- a/src/compositor-fbdev.c
+++ b/src/compositor-fbdev.c
@@ -826,7 +826,7 @@
 }
 
 static struct weston_compositor *
-fbdev_compositor_create(struct wl_display *display, int argc, char *argv[],
+fbdev_compositor_create(struct wl_display *display, int *argc, char *argv[],
                         const char *config_file, struct fbdev_parameters *param)
 {
 	struct fbdev_compositor *compositor;
@@ -897,7 +897,7 @@
 }
 
 WL_EXPORT struct weston_compositor *
-backend_init(struct wl_display *display, int argc, char *argv[],
+backend_init(struct wl_display *display, int *argc, char *argv[],
 	     const char *config_file)
 {
 	/* TODO: Ideally, available frame buffers should be enumerated using