Add script to consolidate variables that only get used once

[matthew-james-brewer]

I made a script that takes the linear list of logic gates and combines them when necessary.

For example:

    ...
    cell g = in_6 & in_1;
    ...
    cell h = in_7 & in_1;
    ...
    cell y = g | h;
    ...
    cell cu = cc | h;
    ...

becomes:

    ...
    cell h = in_7 & in_1;
    ...
    cell y = (in_6 & in_1) | h;
    ...

In other words, it consolidates the gates.

---

Unfortunately, the script is fragile and would break if anything major got restructured in gate.c's generated portion.

However, it offers some insight. For example, it was easy to find ~(~(...)) in the code using this. Also: ... | (0), which also does nothing. Of course, the compiler should remove those, but it's interesting to see.

Note - this is my first pull request.