Add -webcam commandline option to control webcam emulation

-webcam name=<name>[,dir=<direction>] options controls web cameras to use for emulation.

Change-Id: I961fd399c7e041541adda040dd24f194cc383cb9
diff --git a/qemu-options.hx b/qemu-options.hx
index 76432a5..880025e 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1787,4 +1787,7 @@
 DEF("snapshot-no-time-update", 0, QEMU_OPTION_snapshot_no_time_update, \
     "-snapshot-no-time-update Disable time update when restoring snapshots\n")
 
+DEF("list-webcam", 0, QEMU_OPTION_list_webcam, \
+    "-list-webcam List web cameras available for emulation\n")
+
 #endif /* ANDROID */