fmadio_packet.h does not compile with C++

[arghness]

Tested with gcc-14.2.1 on Rocky 9.6.

I wrapped the fmadio_packet.h header with the required dependencies and disabled warnings:

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wignored-qualifiers"
#pragma GCC diagnostic ignored "-Wsign-compare"
#pragma GCC diagnostic ignored "-Wunused-parameter"
#pragma GCC diagnostic ignored "-Wvolatile"

#include "fmadio_packet.h"

#pragma GCC diagnostic pop

However, there were still issues that couldn't be fixed from the command line, missing casts and implicit conversions from u8* to char* which are not allowed in C++.

I put together an example fix in #6 which worked for me.