Revert "Revert "remove some O(n^2) algorithms in the front end" [fix #2270]."

This reverts commit 1396f74efdf9a87d7c2658757f8d2b20885f67c1.
try a different implementation of delete-duplicates
Merge branch 'master' of github.com:JuliaLang/julia into jb/deleteduplicates
Merge branch 'master' of github.com:JuliaLang/julia into jb/deleteduplicates
try another delete-duplicates
Update package listing with new packages
Merge pull request #2399 from aviks/topic/pkglist

Update package listing with new packages
fix #2400, fix #2401
VERSION: 0.2