Move to system (vs autoseeded) RNG on Botan
On Botan we use the autoseeded RNG when on all supported platforms we can use the system RNG. This also works better in a multi threaded environment: on old Botan stateful RNGs including the autoseeded one are not MT safe, on recent (>= 2.16, the last when I write this 2.17.3) versions they are MT safes but for performance it is recommended to make them thread local...
The define to use in the code is BOTAN_HAS_SYSTEM_RNG, include is system_rng.h and the class System_RNG.
BTW IMHO the best should be to use the processor RNG but it is recent and can be tested only at runtime...