[libFuzzer] refactor the code to allow collecting features in different ways. Also initialize a couple of Fuzzer:: members that might have been used uninitialized :(

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288731 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed