Set allow(unstable) in crates that use unstable features
Set allow(unstable) in crates that use unstable features

Lets them build with the -dev, -nightly, or snapshot compiler

bhickey/rand,huonw/rand,retep998/rand,waynenilsen/rand,ebfull/rand,bluss/rand,shepmaster/rand,GrahamDennis/rand,achanda/rand,arthurprs/rand