Adds mineig and maxeig methods

Find smallest and largest eigenvalues for real eigenvalues

Includes specialized method fo SymTridiagonal.
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
Force OpenBLAS to use only one thread to avoid test failures for 32-bit
BLAS on 64-bit architectures.

fix #1804
Update to arpack-ng 3.1.3.
This should fix the depcomp issue on Windows.
Fix a few more arpack filename changes that were missed in the earlier checkin
Revert "reinterpret: scalar reinterpret for Float{32,64} => Uint{32,64}."

This reverts commit eb3fd999b5ebe282715f184016d5546d611f336e.

This functionality already existed; mea culpa.
fix #2733