This eliminates references to lineno and
other globals from ssa conversion.

Passes toolstash-check.

Updates #15756

Change-Id: I9792074fab0036b42f454b79139d0b27db913fb5
Reviewed-on: https://go-review.googlesource.com/38721
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>