The current virRandomBits() API is only usable if the caller wants
a random number in the range [0, n-1) where n is a power of two.
This adds a virRandom() API which generates a double in the
range [0.0,1.0) with 48 bits of entropy. It then also adds a
virRandomInt(uint32_t max) API which generates an unsigned
in the range [0,@max)
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>