Threefish cipher based raw PRN/noise generator.

PURPOSE
	This PRNG is shortened, 32 bit integer version of Threefish-256 block cipher.
	It is technically a 128 bit block cipher with 256 bit key.

	It's purpose is to generate fillers fast, for use in file or disk shredders.
	It is not meant to be secure, i.e. collision/bias free, but it is good at
	generating random noise equal to average output of /dev/urandom, yet much faster.

	Typical performance on Athlon 5000+, x86-32 is about 170M/sec.

	Included tfrand program generates random noise to stdout.

USAGE
	Build example:

		make tfrand

	Test it:

		./tfrand >rng.out

	Measure performance (install tfcrypt first):

		./tfrand | tfcrypt -V.5 -P - /dev/null

	Use libtf.a library in your code, see headers for function references:
	tfe.h: STREAM reference.
	tfprng.h: PRNG reference.

WARNING
	Do NOT use it as cipher! It's just a random block generator.
	You have been warned.

ORIGIN
	This code is derived from tfcipher library.

LICENSE
	Public domain -- free to reuse and adapt.

AUTHOR
	Andrey Rys <rys@lynxlynx.ru>, 17Mar2019.