This change adds fuzzer tests for iLBC, iSAC fix and float, and Opus. The fuzzer function takes a random input vector and splits it into a number of payloads. The lengths of the payloads is also determined by the random vector. The payloads are decoded with the decoders. BUG=webrtc:5306 R=kjellander@webrtc.org, pbos@webrtc.org Review URL: https://codereview.webrtc.org/1499093002 . Cr-Commit-Position: refs/heads/master@{#10932}