`forbid-prop-types`: propWrapperFunctions does not follow identifiers

I fixed a crash from #1253 in 5ad93b4365cc42ff6a6c858fed76b7a2d0c17222.

However, see the [TODO](https://github.com/yannickcr/eslint-plugin-react/commit/5ad93b4365cc42ff6a6c858fed76b7a2d0c17222#diff-f8e412f530183ea4c0e4bbfd3c3f2b0eR408) - the rule (prop-types also) is not following the identifier reference when it's not inline. It should.

cc @dustinsoftware 