Log message:
Move math/R-digest to security/R-digest and fix dependencies.

Note: this commit is part of reorganizing some of the recently
imported R packages, which are being reimported into more appropriate
categories (and removed from math) as a result of a recent discussion
on tech-pkg and privately with wiz@.  See the thread starting with:

  http://mail-index.netbsd.org/tech-pkg/2014/09/05/msg013558.html

Log message:
Initial revision of R-digest v0.6.4.

The digest package provides a function 'digest()' for the creation of
hash digests of arbitrary R objects (using the md5, sha-1, sha-256 and
crc32 algorithms) permitting easy comparison of R language objects, as
well as a function 'hmac()' to create hash-based message
authentication code.