How to add a new pass?

[DJ Delorie]

Ian Lance Taylor <iant@google.com> writes:
> I don't think anybody has ever done this.  At the moment only plugins
> add new passes.  But I agree that backends clearly need to be able to do
> this, and some passes need to move into the appropriate backends.  I
> would encourage you to fix this.

I've done this, to move md_reorg sooner.  The pass gets a "highest" dump
file number, but it runs at the right time.

I just call register_pass() with a suitable struct.