Make sure to update lineStart when incrementing lineNumber in scanTemplate.

As a general rule, whenever we increment lineNumber, we need to set
lineStart to the new value of index, so that column computations (index -
lineStart) will be correct.

https://code.google.com/p/esprima/issues/detail?id=576
Also update lineStart after incrementing lineNumber in scanStringLiteral.

https://code.google.com/p/esprima/issues/detail?id=576