Added fuzzer to integrate Hiredis into OSS-fuzz

[AdamKorcz]

This PR adds a fuzzer that targets redisFormatCommand.

Fuzzing is a method of testing whereby pseudo-random data is passed to an application with the goal of finding bugs and vulnerabilities.

I have worked on running this fuzzer continuously through OSS-fuzz and have set up an integration on the OSS-fuzz side for this. If there is interest in fuzzing Hiredis continuously, all that is needed is for this fuzzer to be merged and at least one maintainers email address on the OSS-fuzz side. This will allow OSS-fuzz to run this fuzzer as well as all future fuzzers continuously, and in case bugs are found, maintainers get notified with an email containing a link to a detailed bug report. The service is free for open source projects and is offered with an implied expectation that bugs are fixed, so that the resources spent on fuzzing Hiredis go towards resolving bugs.

[AdamKorcz]

As mentioned above, I have set up the necessary integration on the OSS-fuzz side here: google/oss-fuzz#4822.

[michael-grunder]

Hi @AdamKorcz thanks for the PR!

This is great. I'm happy to merge this with a couple of tiny changes (mostly formatting and the typecasts I referenced in comments).

Edit: And I'm happy to make the changes, i just want to make sure there aren't technical reasons for the casts.

[AdamKorcz]

Perfect!

I am open to both making the changes myself and you making the changes.

I must admit I don't see any comments in the code at this time.

[michael-grunder]

Apologies, I failed to hit "submit" on the comments.

[AdamKorcz]

Both typecasts have been removed

[michael-grunder]

Merged, thanks!

I'm happy to receive the automatic fuzzing emails.

My email should be public in my GitHub profile and can be found in some hiredis headers