code review 7232071: cmd/cgo: fix line number annotations in generated C code

cmd/cgo: fix line number annotations in generated C code

The old version was using go/ast's CommentGroup.Text method,
but that method drops leading blank lines from the result, so that
if the comment looked like one of

//
// syntax error
import "C"

/*
syntax error
*/
import "C"

then the line numbers for the syntax error would be off by the
number of leading blank lines (1 in each of the above cases).

The new text extractor preserves blank lines.

Fixes issue 4019.

[rsc, 2013-02-01 06:04:38]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go/

[iant, 2013-02-01 15:19:57]

LGTM

[rsc, 2013-02-01 16:34:06]

*** Submitted as https://code.google.com/p/go/source/detail?r=3686735a3658 ***

cmd/cgo: fix line number annotations in generated C code

The old version was using go/ast's CommentGroup.Text method,
but that method drops leading blank lines from the result, so that
if the comment looked like one of

//
// syntax error
import "C"

/*
syntax error
*/
import "C"

then the line numbers for the syntax error would be off by the
number of leading blank lines (1 in each of the above cases).

The new text extractor preserves blank lines.

Fixes issue 4019.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/7232071