Adds mineig and maxeig methods

Find smallest and largest eigenvalues for real eigenvalues

Includes specialized method fo SymTridiagonal.
listen: increase the default backlog to match the Node.js default.
reinterpret: scalar reinterpret for Float{32,64} => Uint{32,64}.
Renames to eigmax and eigmin
close #2719
Merge pull request #2725 from jiahao/maxeig

Adds mineig and maxeig methods
Merge branch 'master' of github.com:JuliaLang/julia into jb/kwargs
support for optional positional and keyword args together
a small optimization