[OCaml] Add missing instruction opcodes to OCaml API

Summary:
The OCaml bindings have become out of date and several opcodes have
been added to the C API without corresponding additions to the OCaml
API.

Reviewers: whitequark, mgorny

Reviewed By: whitequark

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D52196

llvm-svn: 342427