Fix fuzzer_encoder_v2 timeouts

This fixes the 'false positive' oss-fuzz bug filed under
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=47264

The fuzzer was timing out because of an enormous input (932kB)
combined with very slow settings. The commit disables certain
slow settings on inputs larger than 2^18 byte.
1 file changed