go/analysis/passes/printf: return Result for querying func Kind
go/analysis/passes/printf: return Result for querying func Kind

printf.Result has IsPrint function telling the caller if a function is
a Print/Printf function or a wrapper of one.

This aids in developing Ananlyzer's applying checks on Print/Printf
functions.

Implements @alandonovan suggestion from
https://github.com/golang/go/issues/29616#issuecomment-503277625

Change-Id: I203d51f1fcab7d8574d9309c22b404f8e3de43db
GitHub-Last-Rev: 5cb9115d21e89da8e75c5b207bfa1c512c315161
GitHub-Pull-Request: golang/tools#138
Reviewed-on: https://go-review.googlesource.com/c/tools/+/186317
Reviewed-by: Michael Matloob <4562438b12c14e81a47550acde616ff328a909f8@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools