--verbose and --no-timeout options for opt-alive.sh

Add --verbose and --no-timeout options for opt-alive.sh.
Add them to the ReadMe and warn about timeout limitations.
Also add the include file which llvm::PossiblyNonNegInst Class Reference documents, though that wasn’t what broke my build.

I’m not sure how to add tests for this. Some of the infrastructure seems to rely on Python 2, which (no matter how much I miss it), I should probably not install on my work machine.

AliveToolkit / alive2

--verbose and --no-timeout options for opt-alive.sh #964