These fuzzers are meant to be built and executed inside lode.git's sanitizers
environment (currently enables both asan and ubsan).

online.git can be built the usual way, just the additional `--enable-fuzzers`
flag is needed to build the fuzzers. It is useful to do this in a separate
build tree, since the fuzzers config doesn't produce a `coolwsd` binary.

Run the fuzzers like this:

- Admin:

----
./admin_fuzzer -max_len=16384 fuzzer/admin-data/
----

- ClientSession:

----
./clientsession_fuzzer -max_len=16384 fuzzer/data/
----

- HttpResponse:

----
./httpresponse_fuzzer -max_len=16384 fuzzer/httpresponse-data/
----