When debugging a test with 'script/test -D', the DOT-graph generation
code was sometimes causing reallocations that were not captured by the
allocation tracker, because we explicitly disable allocation-tracking
for that method in order to reduce noise when debugging memory leaks.
By growing the relevant array *prior* to turning off allocation
tracking, we can ensure that it is not reallocated within that function,
avoiding false positive memory leak errors.
Fixes#302
* Structure `cli` crate as both a library and an executable, so that
benchmarks can import code from the crate.
* Import macros in the Rust 2018 style.
