closes 16162.

Avoid using file names and file paths for compatibility with
out-of-tree builds.

Note make and ccache don't track blacklist dependencies,
add workarounds.

Document use of coverity, clang static analyzer, and clang dynamic
undefined behavior and address sanitizers in doc/HACKING.

Add clang dynamic sanitizer blacklist in
contrib/clang/sanitizer_blacklist.txt to exempt known undefined
behavior. Include detailed usage instructions in this blacklist file.

Patch by "teor".

Fixes 16152.

This explains that if you change your torrc to do more, you might
need to change tor.service.in to allow it.  See #15195.