set multiple random bits
sometimes don't mangle
fix race at shutdown where we could spawn a new child as the watchdog exited.
collapse single bit setting functions into one
factor out Tavis' random munger into its own function.

And also call it in the 32bit path
give rand64() a 50/50 chance of returning a 32bit number.
Move randbits out of the way of forthcoming work.
use randbits() in rand32
introduce rand8x8

Construct a long made out of 8 bit chunks.
add rept8 random function

generate 8 bit, and copy it throughout a long.
Like rand8x8, but same for every byte.
split up rand32 into generation/mangling
don't take bits away in rand32 mangler
don't always mangle, sometimes let rand32 just pass through
re-use __rand32 in the mangler

This was the reasoning behind splitting it out.
remove duplication in rand64.

Just call rand32 instead of reimplementing it.
add a crappy rand|rand<<32 64bit case
add some 64-bit truncation
Occasionally invert rand64
Increase random distribution in MSB of rand64