Due to a new specification of //line: directives, missing
column info is now treated as column 0, aka "unknown column"
(see https://github.com/golang/go/issues/24183 for details).

As cgo does not add column number to generated //line: directive,
resulting files parsed do not have column info.

Fix by adding column of 1 to generated line directives.

Fixes #26692

Change-Id: Ie9263c0cf666b92d19c34240e745e8f32ffe7174
Reviewed-on: https://go-review.googlesource.com/126675
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>