[OCaml] Add Token type to kind enum in OCaml API

Summary:
The token type has not yet been added to the OCaml API. This
patch only extends the enum, so that e.g. classify_type will not
crash. No support for manipulating or building tokens is added at this
point.

Reviewers: whitequark

Reviewed By: whitequark

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D52197

llvm-svn: 342428