pkg/string_scanner - remove work-around for Issue 17998

[DartBot]

<img src="https://avatars.githubusercontent.com/u/17034?v=3" align="left" width="96" height="96"hspace="10"> Issue by kevmoo
Originally opened as dart-lang/sdk#18469

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It was fixed in https://code.google.com/p/dart/source/detail?r=35368

Need to verify this fix is sufficient.

...and bump the min-SDK to 1.4

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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I want to wait until 1.4 stable is released to do this.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/5479?v=3" align="left" width="48" height="48"hspace="10"> Comment by sethladd

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Is this still a valid issue?

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Set owner to @nex3.
Added Pkg-StringScanner label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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Yes.