Patch polka to define IID_IUnknown, which is needed for using dllcamlidl.so

I used to patch camlidl and put it in my local opam repo, by that was a terrible idea.
2 jobs for master in 5 minutes and 32 seconds (queued for 2 seconds)
Name Stage Failure
failed
test_opam_test Test There is an unknown failure, please try again
  - install ocamlfind     1.7.3     
- install ocamlify 0.0.1
- install ocamlmod 0.0.9
- install ounit 2.0.6
- install rdbg 1.156

The former state can be restored with:
opam switch import "~/.opam/4.05.0/backup/state-20171113101215.export"
ERROR: Job failed: exit code 1