This removes much of the AST logic out of main.go,
and makes it easier to build custom vet binaries
The trade-off in this change is for flexibility.
There's very little change in the per-check files,
a lot less code in main.go (specifically the AST walking
logic has shrunk), and it makes it much easier to build
custom vet binaries simply by dropping new source files
in the directory.
LGTM=josharian, r
R=r, josharian, kamil.kisiel
CC=golang-codereviews
https://golang.org/cl/83400043
It was very ugly; a little tweaking helps godoc parse it better.
Also make unsafeptr.go not own the package doc (add a blank line)
and put one more sentence about that check into doc.go.
Fixesgolang/go#7925.
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/98370044