Remove remove_ignored

[adetaylor]

#288 introduced an analysis pass to remove ignored things (as reported in #288).

I think #373 fixed the root cause, so we should revert #288.

[martinboehme]

I think this may still be needed -- see draft PR #393 for an example where it's necessary to ignore APIs that use other ignored APIs.

[adetaylor]

Turns out you were right all along - see #453! :)

[martinboehme]

Interesting! That was entirely down to luck, not insight on my part though. ;)