This checker needed some reworking because whereas vet sees
unprocessed cgo source files (with partial type information), the
analysis API sees cgo-processed files with complete type information.
However, that means the checker must effectively undo some of the
transformations done by cgo, making it more fragile during changes to
cgo.
Change-Id: I3a243260f59b16e2e546e8f3e4585b93d3731192
Reviewed-on: https://go-review.googlesource.com/c/141157
Reviewed-by: Michael Matloob <matloob@golang.org>
a398e557df