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/android/camera/camera-capture-linux.c b/android/camera/camera-capture-linux.c
index 072d06e..50324f0 100644
--- a/android/camera/camera-capture-linux.c
+++ b/android/camera/camera-capture-linux.c
@@ -1048,6 +1048,9 @@
         if (cd != NULL) {
             LinuxCameraDevice* lcd = (LinuxCameraDevice*)cd->opaque;
             if (!_camera_device_get_info(lcd, cis + found)) {
+                char user_name[24];
+                sprintf(user_name, "webcam%d", found);
+                cis[found].display_name = ASTRDUP(user_name);
                 cis[found].in_use = 0;
                 found++;
             }