Clang source-based code coverage with fuzz test

[xis19]

It seems clang supports source-based code coverage tool, if it is possible to map flow-generated code back to original code, we may not need to handle our own set of macro-based coverage tool which brings extra complicity.

[jzhou77]

This is interesting, but may not completely cover what CODE_PROBE does. For instance, CODE_PROBE macro has more features like checking different conditions, e.g.,

			CODE_PROBE(quarantine, "Quarantining TSS because it got mismatch");
			CODE_PROBE(!quarantine, "Killing TSS because it got mismatch");