[libFuzzer] remove the data-flow-trace (DFT) python scripts; their functionality is now part of libFuzzer proper; also write functions.txt to the disk only if this file doesn't exist yet

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer@361452 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed