Add test for consecutive newlines in string node.
Add test for consecutive newlines in string node.

SourceNode should skip over all newlines in the node, but it
currently skips every other consecutive newline. This is due to RegExp
behaviour with the 'g' flag - the RegExp object will track its
position in successive calls to `test` (or `exec`) for the same string.

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec#Example.3A_Finding_successive_matches

stealjs/source-map,ejpbruel/source-map,garysye/source-map,garysye/source-map,azakhary/source-map,webcoding/source-map,bitovi/source-map,modulexcite/source-map,bitovi/source-map,spark/source-map,ejpbruel/source-map,modulexcite/source-map,azakhary/source-map,spark/source-map,webcoding/source-map,stealjs/source-map