Note: the previous rev's CVS comment was messed up due to an editor snafu.

Note: the previous rev's CVS comment was messed up due to an editor snafu.

/dev/random was almost always returning 0 bytes.  This was due to several
factors, primarily the fact that the stack smash handler reads 32 bytes from
/dev/urandom every time a program is exec'd, and because /dev/random and
/dev/urandom share the same pool.

* Give /dev/random and /dev/urandom their own separate pools.

* Be slightly less conservative on the number of bits of randomness we
  think we've added.

* extract_entropy() calls add_timer_randomness(), which adds entropy.  This
  can create a situation where entropy always appears to be available when,
  in fact, it is of very low quality.  Add a little hysteresis so degenerate
  cases return 0 bytes instead of 1 byte.

* Also (in this commit) fix a bug in the previous commit where the randomness
  added was accidently halved.

Reported-by: David Rhodus