Cryptography_add_osrandom_engine should be safe to call multiple times
test to confirm calling Cryptography_add_osrandom_engine > 1 is safe
clear the error you get if you get a NULL engine back
add a comment to explain this damn function
c89, thanks microsoft...
Merge pull request #660 from reaperhulk/osrandom-more-robust

Cryptography_add_osrandom_engine should be safe to call multiple times