Testing removal of ifdef or configure checks

#ifdef removal is risky

Large-scale removal of "unused" ifdef is an important, but risky task.

It is difficult (and time consuming) to prove that the code is unused and that there is no change to the compiled output.

A script to help

This script wraps gcc -E to attempt to solve this dilemma, so as to provide a result that can be reasoned with via tools like dirdiff