Assert that code does not cause growth in memory usage
Description
This module provides a function to check that a given block of code does
not result in the process consuming extra memory once it has finished.
Despite the name of this module it does not, in the strictest sense of the
word, test for a memory leak: that term is specifically applied to cases
where memory has been allocated but all record of it has been lost, so it
cannot possibly be reclaimed. While the method employed by this module can
detect such bugs, it can also detect cases where memory is still referenced
and reachable, but the usage has grown more than would be expected or
necessary.
