Give an error if the server was closed while blocked in accept
isperm using a BitVector indicating which values have been seen
Fold _invperm back into invperm; add tests
Merge pull request #4421 from JuliaLang/db/isperm

isperm without determining the inverse permutation
Further changes to eigs

(1) ARPACK info flag 1 now results in a warning (maximal number of
iterations taken) rather then throwing an error.
(2) Added the return value nconv, indicating the number of converged
eigenvalues, which is relevant when the maximal number of iterations
has been taken before all requested eigenvalues have converged (which
no longer leads to an error thanks to (1) ).
(3) Modified behavior of eigs such that any input type of matrix is
allowed, as long as the type of A overloads the methods size, issym,
eltype and can be multiplied with a vector of the same element type.
(4) Updated test file accordingly