ctlib example

[yhql]

This PR attempts to minimize the operations needed to handle a checkct-generated project.

checkct was not modified to generate the new examples in this PR, which are only here to show how this would work.
A new checkct project (like the new top-level chachapoly and dalek examples) generates a project that "hides" all binsec invocation parameters in the runner part of the project configuration, turning it into a normal cargo runnable project.
It only needs a single main.rs file because the randomness generation part was made available through a new ctlib that is a dependency of the generated project.
checkct is also a build-dependency of the generated project, and can generate the binsec driver from there. The template for this driver was slightly modified to reduce dependencies to machine-specific setup (no more setting up the return address manually for example)