test: Add an example program to create a virtual UMP Endpoint

test: Add an example program to create a virtual UMP Endpoint

Provide an example program to demonstrate how to create a UMP Endpoint
and Blocks, i.e. a virtual UMP device.

It's a simple filtering application that just haves the incoming note
on/off velocity and sends out to the output.  The UMP Endpoint and
Block attributes can be adjusted via command-line options.

Signed-off-by: Takashi Iwai <tiwai@suse.de>