* mpg123: limit runtime of decode_fuzzer
To avoid spurious timeout reports, the test shall end after 10000 MPEG frames
or 1 MiB of data, which should both be reasonable numbers. The timeout
report motivating this had 500K with 140k bad frames. The limit of
10000 frames corresponds to a normal radio song as MP3 stream.
* mpg123: limit runtime of read_fuzzer
This applies the same logic as the decode fuzzer: stop decoding after
10000 MPEG frames or 1 MiB of input data. We could debate a bigger
limit on the data size, but we do want compact testcases, right?
* mpg123/read_fuzzer: disable error messages from libmpg123
This shall remove any error messages libmpg123 prints out during fuzzing,
leaving only the crash trace at the inevitable end.