add sancov-like allow/denylist instrument feature

README.md

TODO.md

docs/Changelog.md

docs/FAQ.md

docs/env_variables.md

docs/perf_tips.md

gcc_plugin/GNUmakefile

gcc_plugin/Makefile

include/envs.h

llvm_mode/README.instrument_list.md

llvm_mode/README.lto.md

llvm_mode/README.md

llvm_mode/afl-clang-fast.c

llvm_mode/afl-llvm-common.cc

llvm_mode/afl-llvm-lto-instrumentlist.so.cc