fix std::cmp docstring
update FuzzyEq to explicit self
add a FuzzyEq method that accepts an epsilon value
implement fuzzy_eq with fuzzy_eq_eps
Merge pull request #4664 from thestinger/fuzzy

FuzzyEq improvements
testsuite: Xfail file that I added by mistake
Fix licenseck to allow 2012-2013 as the year range
fix FuzzyEq
libsyntax: De-export a lot of libsyntax. rs=deëxporting
Merge pull request #4676 from thestinger/fuzzy

fix FuzzyEq
treemap: rm a bit of redundant code
update comments documenting issue #4492 workaround
add is_subset and is_superset to the Set trait
add is_disjoint to the Set trait