Build on Ubuntu 22.04

[devio-at]

If make fails with

fatal error: alsa/asoundlib.h: No such file or directory

use make noalsa instead. (yes, that's in the readme already)

make issues many warnings

warning: ISO C++17 does not allow ‘register’ storage class specifier [-Wregister]

editing the Makefile to read

CFLAGS = -Wall -Wregister

fixed the warnings.