force register* before actually using input and output streams

[GassaFM]

If one forgets registerTestlibCmd or the like, the input and output streams are in some unspecified state. It would save developer time to have a clear error when such stream is used before registering.

[GassaFM]

One way to do it is to use macros for register* commands which change streams' internal state. Another approach is to initialize the streams with something bad which, when used, manifests clearly and immediately.

[stgatilov]

And if one forgets to register generator, then random seed seems to not be set from cmd arguments. As a result, stress-testing with such generator may be a waste of time.

[MikeMirzayanov]

Fixed ages ago