igb: enable MSI-X for i354 on C2550 SoC
glxsb(4) - use add_buffer_randomness()
kernel - add ChaCha algorithm (djb's merged implementation)
kernel - add a fortuna-based CSPRNG

 * This implements a Fortuna-based CSPRNG.

 * All entropy pools are shared across all CPUs in the system.

 * SHA256 is used instead of SHA256_d as cryptographical hash
   function.

 * ChaCha is used as stream cipher instead of AES in CTR mode.
Add ChaCha and CSPRNG to conf/files
kern_nrandom, rnd drivers: update for new CSPRNG

 * Identify each source of entropy with an identifier, so that
   for example the Fortuna CSPRNG can manage the pool index
   for each source.

 * Add a new sysctl, kern.rand_mode, which can be used to select
   which generator is used for /dev/random; valid values are:
    - csprng (to use only the Fortuna-based CSPRNG)
    - ibaa (to use only IBAA)
    - mixed (to XOR both csprng and ibaa in the output stream
   It defaults to "mixed".
random.4 - update for new CSPRNG status