L2Program/FlintPlusPlus — pull request #40 by kanielc (2014-05-25 21:09:33+00:00)
Title: Replace Whitespace string with StringFragment

Token currently has a constructed string indicating the preceding
whitespace. Since this is contiguous and found in the input stream,
we can just use a StringFragment.

This delivered a very nice performance increase, as we avoid allocating
a ton of strings.

(The run against folly+gtest+double_conversion is now down to 1 second,
even with all the new checks that we added).