A few days ago ossfuzz stoped testing new FFmpeg as it run out of diskspacee

https://oss-fuzz-build-logs.storage.googleapis.com/index.html

An alternative would be to revert the API.

This changes for example
-rwxr-x--- 1 michael michael 144803654 May 14 12:54 tools/target_dec_ac3_fixed_fuzzer*
to
-rwxr-x--- 1 michael michael  30333852 May 14 12:51 tools/target_dec_ac3_fixed_fuzzer*

Which should massively decrease space requirements
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>