This CL updates the importer to match the original code in the std lib
but for the necessary changes to make the code work in x/tools and
with older versions of the std lib.
Notably, it brings over changes from:
https://go-review.googlesource.com/c/152078https://go-review.googlesource.com/c/152077https://golang.org/cl/151997https://golang.org/cl/151557https://golang.org/cl/149957
including test fixes (we want tests to run when gccgo is available,
not just when all go tools are gccgo-based), bug fixes (primarily
related to aliases), performance enhancements, and new code to read
the V3 export data emitted by the most recent gccgo.
Change-Id: I2d34bace23769e62795599b93db8295169076594
Reviewed-on: https://go-review.googlesource.com/c/151717
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>