btnplr, a simple player

[Hannu]

Dear VS1010 users,

Here is a small player program. It itakes filespec, plays the files in loop and if too many loops or too long without user input, VS1010 powers down. User can interact with buttons or UART.

This is tested with developer board and one button was too slow to read when playing from SPI flash, so it is disabled. If you intend to design your own board, take care of boot modes and use user buttons in different pins than SPI0

And as always, bug reports are welcome.