R: deprecate ARPACK function

[gaborcsardi]

From @gaborcsardi on June 7, 2014 16:57

Because there is also https://github.com/yixuan/rARPACK

Copied from original issue: igraph/igraph#631

[szhorvat]

Targeting complete removal for igraph 2.0. Providing an ARPACK interface is not in scope for igraph. The RSpectra package provides an almost complete replacement.

[maelle]

Does this mean only arpack() or other functions too?