Allow setting device name by command line argument.

[vaguerant]

The device name for the device cec-client is running on appears to be hardcoded (see below). A command line argument like -n "Your Name Here" (truncated to 13 bytes or 14 once #333 is fixed) would be very useful to me and hopefully others.

libcec/src/cec-client/cec-client.cpp

Line 1233 in 8adc786

snprintf(g_config.strDeviceName, 13, "CECTester");