overlay: Allow simple positioning and resizing

Using window.size=<width>x<height> or window.size=<scale>% in
the config file, or --size=<scale>% or --size=<width>x<height>

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/overlay/overlay.c b/overlay/overlay.c
index 03e6ada..acbd853 100644
--- a/overlay/overlay.c
+++ b/overlay/overlay.c
@@ -740,6 +740,7 @@
 		{"config", 1, 0, 'c'},
 		{"geometry", 1, 0, 'G'},
 		{"position", 1, 0, 'P'},
+		{"size", 1, 0, 'S'},
 		{NULL, 0, 0, 0,}
 	};
 	struct overlay_context ctx;
@@ -751,7 +752,7 @@
 	config_init(&config);
 
 	opterr = 0;
-	while ((i = getopt_long(argc, argv, "c:f", long_options, &index)) != -1) {
+	while ((i = getopt_long(argc, argv, "c:f:", long_options, &index)) != -1) {
 		switch (i) {
 		case 'c':
 			config_parse_string(&config, optarg);
@@ -762,6 +763,9 @@
 		case 'P':
 			config_set_value(&config, "window", "position", optarg);
 			break;
+		case 'S':
+			config_set_value(&config, "window", "size", optarg);
+			break;
 		case 'f':
 			daemonize = 0;
 			break;