Changelog for raaz-0.2.1

Change log for raaz.

This is a minor release just to get the latest ghc.

Some cpu detection builtin for GCC. Would come handy in future for selection of primitives are runtime.
BLAKE2b, BLAKE2s added.
system entropy: Experimental support for linux getrandom call
removed depreciated liftSubMT from Memory.
Got rid of the class MemoryMonad, instead introduced a more specific MemoryThread. This allows to treat monads like RT mem much like MT mem, including possibility of running an action on a sub-memory.
combinator to randomise memory cells.
hardened the prg so that a compromise on the current prg state will not expose previously generated data.
OpenBSD/NetBSD: fix incorrect arc4random call.
Basic Unix man-page for the raaz command.
Windows support is now included. The missing pieces were system entropy and memory locking which is now available.

Stream cipher chacha20 added.
Added a PRG that uses chacha20, seeded with system entropy
Sha1 highly depreciated in view of reported collision.
We now have super command raaz with subcommands
- checksum: as a replacement for the old checksum executable
- rand: for generating random bytes.

Low level changes

Reworked alignment considerations.
- New Alignment type
- Ways for implementations to demand that the input buffer be aligned (mainly to facilitate more efficient SIMD implementations).
Num instance from LengthUnit removed, Monoid instance added (See issue:#247)

This release comes with very little changes.