generalized and more efficient cat implementation
need to initialize new gc root in jl_compute_type_union
add helpful quotes to some error messages. closes #8837
Fix #6804

floor(2^31-1*runif(1)) was always returning the value 2147483647. It is now floor(runif(1, min=0, max=2^31-1))
Merge pull request #8841 from pabloferz/pf/perf

Fix #6804
NEWS updates
some cleanup in datafmt

clarify docs for the is_valid_* functions
add isless(::Char, ::Char) method (required for sort), add test
clarification
Merge pull request #7600 from Jutho/jh/cat

generalised and improved cat implementation
Make travis complain about whitespace errors in the last 10 commits