Streaming: Remove any pointer BUrl argument

* There's no need to pass BUrl by pointer, this is
potentially dangerous and leaky without any advantage,
copying is definitely safer.

streamer_sniff_test: Little improvements

* Print tracks detected count.
* Delete media file before to exit.

Add streamer_sniff_test

* This is a simple test that open an url for streaming using
BMediaFile, the purpose is to test if streamers sniffing work
well.