MAINT integrate/odepack: kill dead Fortran code

I was checking out compiler warnings again and this time I found out we ship and build at least 6 kLOC of dead Fortran code in `scipy/integrate/odepack` (a lot of it comments, but not the kind that I can understand). I took the liberty of removing some of it.

It seems the code wasn't pristine anyway: it carries on `index` file that doesn't match what is there.